When you are trying to conceive, blood tests become part of the landscape. Low AMH and high FSH often raise unnecessary fears about future fertility.

They can be clinically important. They can affect treatment planning and, depending on your age, menstrual history and wider fertility picture, they can make time more important. But they answer different biological questions. Neither result establishes that a follicle cannot mature, ovulate, be fertilised or lead to pregnancy.

What AMH actually measures — and why it is not a measure of ovarian reserve

AMH is commonly described as an ovarian reserve test. In practice, it is not a direct measure of how many eggs remain.

Ovarian reserve is a theoretical concept. It refers to the number of oocytes remaining in the ovary. It cannot be directly measured — only inferred.

AMH is produced by granulosa cells of small growing follicles. It tells us how the ovary is behaving right now and how it is likely to respond to stimulation in IVF. It does not measure egg quality, or how likely pregnancy is in a given cycle.

AMH tells us how the ovary is behaving right now — not how many eggs remain.

Low AMH is often misunderstood — and it can lead to the wrong treatment decisions

If you’ve been told your AMH is low, you may have been moved toward treatment before understanding what it actually reflects.

This guide walks through what your AMH results actually reflect and what they mean for your fertility decisions. 

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What FSH actually measures

FSH is not produced by the ovary. It is produced by the pituitary gland.

Early follicle growth begins independently of FSH. FSH supports growth at later stages, including growth of the antral follicle cohort.

As those follicles grow, they produce inhibin B and oestradiol. This feeds back to the pituitary to lower FSH. When inhibin B declines, that feedback weakens and basal FSH rises.

A single FSH reading can fluctuate significantly between and within cycles, which limits what one result can tell us.

Why low AMH and high FSH often appear together

AMH is more sensitive and tends to decline before FSH rises. Basal FSH is a specific but not sensitive marker. Because it fluctuates, a single value can be misleading.

When AMH is low and basal FSH is high on appropriately timed testing, it suggests reduced current follicular activity. In IVF, that helps predict how many eggs may be retrieved. It does not establish that pregnancy is not possible.

What low AMH and high FSH do not establish

If you’ve just been told you have low AMH and high FSH, it’s completely understandable to feel panicked. Many women are told this means they can’t get pregnant, or that time has run out. That is not what these results mean.

For women who don’t have a known diagnosis of infertility, ovarian reserve markers were poor predictors of reproductive potential. They describe how the ovary is behaving right now, not whether this month’s egg can become a pregnancy.

In fact, women with low AMH or high FSH had similar pregnancy rates after 6 and 12 cycles compared to women with normal levels.

And longer term, women defined as having low AMH or high FSH did not have a lower chance of future live birth >3 years after testing and did not have a higher risk of future infertility.

Ovulation needs one egg, not many. These markers describe the current pool and the feedback to the brain — not whether the egg you release this month is capable of resulting in pregnancy.

Which is why results should not be used to deter or refuse treatment.

IVF response is not fertility capacity

IVF depends on recruiting multiple follicles at once. Natural conception and IVF share important requirements — including a competent egg — they simply ask the ovary to do different things in that cycle.

AMH and antral follicle count have been well demonstrated to predict oocyte yield in IVF. Elevated basal FSH is specific but not sensitive, and its variability limits the reliability of a single measurement.

When AMH is low, stimulation may be less efficient. That can mean fewer eggs retrieved in that cycle. In one IVF study, cancellation rates were significantly higher among patients with low AMH, and highest when both markers were abnormal. This was a study-specific finding — individual outcomes vary.

This reflects a limitation of a treatment that relies on multiple follicles, not a verdict on whether pregnancy is possible.

When low AMH and high FSH does make time more important

Age remains the strongest determinant of egg quality. Menstrual history matters — progressive shortening of cycle length or new irregularity can provide context that a single blood test cannot.

A low AMH with high FSH at 32 with regular cycles is a different clinical scenario to the same results at 41 with shortening cycles. The numbers are the same. The biological context is not.

A more proportional way forward

Low AMH and high FSH are not meaningless — but they are not predictive in the way many people are led to believe.

• Useful in IVF planning.
• Limited in predicting natural conception.
• Insufficient on their own to establish that pregnancy is not possible.

Single numbers should not be asked to carry life-changing weight.

Finding a way forward with targeted nutrition

Follicles are metabolically active structures providing the energy and nutrients your egg needs while it is maturing, ready for fertilisation. After ovulation, the follicle becomes the corpus luteum, which produces progesterone to support the endometrium in early pregnancy. The development of an egg towards ovulation takes place over several months.

Sperm development also takes close to three months, which is why preparation is framed around a similar window for both partners.

That window is the period when follicles are drawing on energy, nutrients and hormonal signals to mature — which is why meals, nutrient intake, sleep and metabolic health are central to preparation during this time.

The Now Baby 90-Day Low AMH Nutrition Protocol is professionally designed around that window — nutrient-dense, blood sugar-balancing, and deliberately constructed to support the cellular conditions that egg and sperm development depend on.

Get the Complete Nutrition Protocol for Low AMH

PIO Shots vs Progesterone Suppositories for FET: Is One Better?

PIO shots and progesterone suppositories are two progesterone routes used in frozen embryo transfer cycles.

PIO stands for progesterone in oil. It is usually given as an intramuscular injection.

Progesterone suppositories are progesterone medication administered via the vagina in frozen embryo transfer cycles.

Neither route is automatically better in every FET cycle. They deliver progesterone differently, and each route belongs inside a wider protocol that includes dose, timing, embryo stage, cycle type and clinic monitoring.

The comparison starts with the job progesterone is doing.

In FET, progesterone is used to move the endometrial lining from oestrogen-led growth into the receptive phase needed before your embryo is transferred.

A lining can look thick enough on scan and still need the correct progesterone exposure before transfer. Thickness is structure. Progesterone changes function.

It affects timing, secretions, gene activity, tissue response and the opening of the implantation window.

That is why the route cannot be judged on its own.

PIO and suppositories are not two simple strength levels. They are two delivery routes for the hormone your lining needs to be exposed to at the right time.

Why progesterone support matters in FET

In an ovulatory cycle, progesterone rises after ovulation.

That rise comes from the corpus luteum, the temporary hormone-producing structure left behind after the follicle releases the egg.

Before ovulation, oestrogen helps the endometrial lining grow. After ovulation, progesterone changes the lining from a growth phase into a secretory, receptive phase.

The lining is not simply becoming thicker.

It is changing what it can do.

Progesterone changes the glands within the endometrium. It affects the molecules released into the uterine cavity. It helps regulate the timing of the implantation window, when the lining is most able to respond to an embryo.

That timing is central to FET.

In a fully medicated FET, ovulation is usually suppressed or bypassed. The body’s usual post-ovulation progesterone source is not providing the main support, so the clinic has to prescribe and time progesterone deliberately.

In a natural or modified natural FET, ovulation may create a corpus luteum. Your clinic may still prescribe progesterone support to strengthen or standardise the luteal phase around transfer.

The protocol is designed to line up two things:

your embryo’s stage of development

and your lining’s progesterone exposure.

A blastocyst is not transferred into a lining that has only just started receiving progesterone. The clinic counts progesterone exposure because the lining changes over time.

Too little exposure can leave the lining behind the embryo.

Too much exposure can move the lining ahead.

The timing matters.

This is why progesterone instructions are not background medication. They are part of the transfer protocol itself.

How PIO shots deliver progesterone

PIO works through systemic progesterone exposure.

The progesterone is carried in oil, so it does not move into the bloodstream all at once. After the injection, the oil base holds progesterone in the muscle and releases it gradually into the circulation.

From there, progesterone reaches the uterus through the blood supply.

The endometrial lining has progesterone receptors. Once the lining is exposed to progesterone, the cells in that tissue begin to behave differently. The glands become more secretory. The lining becomes more closely timed to the embryo stage. The implantation window begins to open according to the number of progesterone exposure days before transfer.

In a fully medicated FET, this matters because ovulation is usually suppressed or bypassed.

There may be no corpus luteum providing the body’s usual post-ovulation progesterone rise. The clinic is creating that hormonal phase with medication.

PIO gives the clinic a systemic route for that support.

If serum progesterone monitoring is used, the blood result gives one measure of circulating progesterone. It does not show every detail of how the lining is responding, but it can help the clinic assess progesterone exposure within its own protocol.

The injection route can be physically difficult.

The oil base can irritate muscle tissue and leave soreness, bruising, tenderness, swelling or small lumps. These effects can make the cycle harder to tolerate, especially when injections are daily.

That physical load is real. It affects comfort and tolerance during the cycle.

Within the FET protocol, PIO’s job is progesterone exposure over time. It provides a bloodstream route for the hormone that helps the endometrium move into the progesterone-led phase planned before transfer.

How progesterone suppositories deliver progesterone

Vaginal progesterone does not rely on the same bloodstream route as PIO.

After insertion, progesterone is absorbed through the vaginal tissue. From there, it can reach the reproductive tract through local blood vessels and tissue pathways close to the uterus.

That closeness matters.

With PIO, progesterone enters the wider circulation first and then reaches the uterus through the blood supply.

With vaginal progesterone, the route is more local. The uterus can be exposed to progesterone even when the level measured in the bloodstream does not look the same as it might after an intramuscular injection.

This is why the two routes should not be compared as if they are simply stronger and weaker versions of the same delivery method.

They move progesterone through the body differently.

For the endometrial lining, the key issue is still progesterone exposure over time.

The lining has progesterone receptors. Once those receptors are exposed to progesterone over the planned number of days before transfer, the tissue begins to move into the progesterone-led phase needed for a frozen embryo transfer.

The glands in the lining become more secretory. The tissue becomes more closely timed to the embryo stage. The implantation window is shaped by that timed exposure before transfer.

Vaginal progesterone gives the clinic a local route for creating that exposure.

With suppositories, progesterone reaches the reproductive tract through vaginal absorption rather than first moving from muscle into the wider bloodstream.

That local route is why blood progesterone levels may not mirror PIO, even when the uterus is being exposed to progesterone.

Why clinics choose different protocols

Progesterone protocols vary because FET cycles are not all built the same way.

In a fully medicated FET, ovulation is usually suppressed or bypassed. The clinic has to create the progesterone phase with medication because there may be no corpus luteum providing the body’s usual post-ovulation rise.

In a natural or modified natural FET, ovulation may still happen. The corpus luteum may contribute progesterone, and medication may be added to support or standardise the luteal phase around transfer.

Those are different hormonal starting points.

Embryo stage also matters. A blastocyst transfer is timed around a defined number of progesterone exposure days before transfer. The lining and embryo need to be matched in time, not just brought together in the uterus.

Monitoring policy adds another layer.

Some clinics check serum progesterone before transfer. Some adjust support if blood levels fall below their threshold. Others use a standard protocol based on cycle type, medication route and their own outcome data.

Route choice sits inside that wider system.

PIO gives progesterone through a systemic bloodstream route. Vaginal progesterone gives a more local route close to the reproductive tract. A combined protocol may be used when a clinic wants both forms of exposure or when previous monitoring has raised concern.

That does not make one route the universal answer.

It means the route only makes sense when the full protocol is considered: whether ovulation occurred, whether a corpus luteum is present, when progesterone started, how many exposure days the lining has before transfer, what embryo stage is being transferred and whether the clinic is monitoring progesterone levels.

This is why route choice cannot be separated from cycle design.

A medicated FET without a corpus luteum, a natural or modified natural FET with one, a monitored cycle with serum progesterone thresholds, and a blastocyst transfer timed to defined progesterone exposure days are not the same clinical situation.

The protocol is built around those differences.

What you can support during the implantation window

By transfer day, progesterone has already been doing a specific job.

It has helped prepare the endometrial lining. The lining is not being prepared for thickness alone. It is being timed for contact with your embryo.

Embryo transfer then places your embryo into the uterus.

The 5 phases of implantation come next.

Secure implantation into the lining, early blood supply, gene expression and differentiation, placental formation and immune adaptation.

Secure implantation into the lining is first contact becoming more than contact.

The blastocyst has to settle against the endometrial surface. Cells on the outer layer of the embryo attach to the lining and begin moving into the upper layer of maternal tissue. The lining has to remodel around that contact, so your embryo is not simply resting in the uterus. It is beginning to embed.

Early blood supply has to start developing around that interaction.

Progesterone helps prepare the lining for this window.

The implantation process itself uses nutrients to support cell division, tissue remodelling, blood-supply signals, gene activity, early placental tissue development and immune activity adaptation.

That is the part nutrition can support.

Nutrition provides the building blocks for this critical phase.

The progesterone protocol prepares and supports the lining.

The days after transfer ask more of the body than lining preparation alone.

Nutrients for life

Each of the five implantation phases has a specific nutritional demand. The fourteen days after transfer are when those demands are active. This is not a window where general healthy eating or supplements are enough.

The Now Baby FET Implantation Meal Plan is built around exactly that window. Every meal across the fourteen days has been designed around the nutritional demands of the implantation window — every process, every nutrient, every day — professionally analysed and structured so that the one variable that remains within your control is no longer left to chance.

You have optimised everything your clinic controls. This is the part only you can do.

Get the FET Implantation Support Meal Plan.

For you frozen embryo transfer, progesterone replaces the hormone signal that would usually come from ovulation.

In a natural cycle, ovulation creates the corpus luteum, a temporary hormone-producing structure that releases progesterone after the egg has been released. Progesterone then helps the uterine lining move into the receptive phase, where implantation can begin.

In a medicated FET, ovulation is usually controlled or bypassed, so the clinic provides progesterone as medication. This gives the lining the progesterone exposure it needs before the embryo is transferred.

That is why timing matters. The number of days on progesterone helps your clinic align the stage of the embryo with the stage of the uterine lining, so transfer happens inside the intended implantation window.

Why progesterone matters in a frozen embryo transfer

Progesterone turns a medicated FET into a scheduled clinical process.

Once progesterone begins, your transfer date is tied to the number of days your lining has been exposed to it. This is especially important for a blastocyst transfer, because the embryo has already developed for several days before freezing.

Your clinic is aiming for synchrony: an embryo at the right stage meeting an endometrium in the right phase.

That is why progesterone instructions are usually exact. The dose, route and timing all belong to the protocol. Vaginal pessaries, injections, tablets or combinations may be used depending on the clinic and individual plan.

For the patient, this means progesterone is more than “support.” It is part of how the transfer is scheduled, protected and interpreted.

What progesterone does to the uterine lining

Before progesterone begins, oestrogen is often used in a medicated FET to help build the uterine lining. Progesterone then changes the lining from a growth phase into a receptive phase.

This matters because implantation involves more than lining thickness. A lining can measure well on scan, but the hormonal phase of the lining also needs to be right.

Progesterone helps the lining become secretory. In simple terms, the lining moves from building mode into receiving mode.

During this phase, the endometrium becomes more prepared for embryo signalling, attachment and early communication. This is the environment your clinic is trying to create before transfer.

The scan tells your clinic about lining appearance and thickness. Progesterone exposure helps determine the timing of receptivity.

Progesterone symptoms reflect medication response

Progesterone can create strong body sensations during the transfer window.

Common symptoms include breast tenderness, bloating, constipation, tiredness, mood changes, pelvic heaviness, discharge, nausea or cramping. Some people feel very symptomatic. Others feel very little.

Both patterns are common during progesterone support.

This is one reason the two-week wait can feel so difficult. The medication can create sensations people associate with early pregnancy, while early pregnancy itself may produce few clear signs at this stage.

Symptoms are real body signals, but they are usually medication signals rather than reliable implantation evidence.

A pregnancy test or blood test gives your clinic the information needed to interpret the outcome.

What low or missed progesterone can mean

Progesterone timing has clinical importance in a medicated FET.

Some studies have linked lower progesterone levels around transfer with lower pregnancy outcomes, although clinic protocols and testing approaches vary. Some clinics monitor progesterone blood levels and adjust support where needed. Others use standardised dosing based on their own protocol.

The route of progesterone also matters. Vaginal progesterone can create strong local exposure in the uterine area, while injections may produce different blood levels. This is one reason clinics may interpret progesterone results differently depending on the medication used.

A missed dose deserves clinic guidance. The safest next step is to contact your clinic and follow their instruction for your protocol.

They may advise you to take the dose when remembered, adjust timing, or continue with the next scheduled dose. The right answer depends on the medication type, dose, timing and stage of your transfer cycle.

Medication decisions during FET belong with the clinic managing the protocol.

When to contact your clinic

Contact your clinic promptly with medication concerns during a frozen embryo transfer cycle.

This includes a missed progesterone dose, the wrong dose, running out of medication, vomiting after oral medication, uncertainty about timing, heavy bleeding, severe pain, or confusion about whether to continue progesterone.

Your clinic knows your embryo stage, transfer date, medication route, dose and monitoring results. Those details matter when deciding what to do next.

Forum answers and symptom lists can feel reassuring in the moment, but progesterone decisions need protocol-specific advice.

During a medicated FET, progesterone is part of the transfer plan. Your clinic should guide changes to that plan.

How to support the transfer window while taking progesterone

Progesterone helps time the lining for transfer, but implantation itself is more than one moment.

After transfer, the body is supporting several linked processes:

• A receptive lining — the endometrium needs to stay in the right phase.
• Early attachment — the embryo and lining begin communicating.
• Blood flow support — oxygen and nutrients need to reach the implantation site.
• Immune balance — the immune system needs to support implantation calmly.
• Early placental signals — the first steps toward pregnancy signalling begin.

Progesterone helps create the hormonal conditions for this window. Nutrition supplies the metabolic stability, protein, healthy fats, and micronutrients your body uses while this work is unfolding.

The Now Baby FET Implantation Support meal plan takes all the guesswork and macro counting out of it for you.

Starting the day after transfer, it gives you a clear nutrition structure for the implantation window; balanced macros, targeted nutrient and meals designed to support successful implantation.

Your clinic manages the progesterone protocol. The Now Baby FET Implantation Support meal plan gives you the nutrition structure progesterone cannot provide: balanced macros, steady nourishment and clear daily meals from the day after transfer through the two-week wait.

FET Implantation Meal Plan

Your clinic maps your progesterone protocol.

The Now Baby FET Implantation Support meal plan maps your nutrition from the day after transfer through the implantation window.

With balanced macros, targeted nutrients and professionally developed daily meals for the implantation window, it takes all the guesswork out for you.

Get the FET Implantation Support Meal Plan

Progesterone suppositories are progesterone medication administered via the vagina in some frozen embryo transfer cycles.

Your clinic may prescribe them before embryo transfer, after embryo transfer, or both, depending on your own protocol.

A suppository is designed to soften after insertion. Progesterone is released as the base softens and is absorbed via the vaginal wall. Some of that softened base can then mix with vaginal fluid and appear later as discharge or residue.

That residue can look like medication has leaked out and you may be concerned that your dosage is affected. Seeing residue does not mean the progesterone dose has failed.

Why clinics prescribe progesterone suppositories in FET

In an ovulatory cycle, progesterone rises after ovulation.

That rise matters because progesterone helps move the endometrium into the receptive phase needed for implantation.

A fully medicated FET protocol is different.

Ovulation is usually suppressed, so there is no corpus luteum providing progesterone for the lining. The cycle does not create its own post-ovulation progesterone rise.

Progesterone medication replaces that missing source.

This is why progesterone may be started before embryo transfer. The lining needs progesterone acting on it before your embryo is placed into the uterus. Progesterone is usually continued after transfer because the endometrium still needs progesterone support while the embryo and lining move into the implantation window.

Progesterone suppositories are one option for providing that medication. Some cycles use vaginal progesterone alone. Others use more than one progesterone form.

The reason is the same: the lining needs progesterone before transfer and continued progesterone support after the embryo is placed into your uterus.

Discharge and leaking after progesterone suppositories

Progesterone suppositories soften after insertion.

As the base softens, progesterone is released and absorbed through the vaginal wall. Some of the softened base can then mix with vaginal fluid and appear later as discharge or residue.

That residue can look like leaking. It may look white, creamy, chalky, oily or watery. It may show on underwear, a liner or tissue, appear when you wipe, or become more noticeable after standing, walking, changing position or using the toilet.

Movement can make residue more noticeable. Softened base that has been sitting in the vagina may move down and appear on a liner, tissue or underwear.

The amount can vary from dose to dose. One dose may leave very little residue. Another may leave a heavier mark.

More visible residue does not reliably mean that less progesterone has been absorbed. It usually means more softened base and vaginal fluid have moved out after the suppository has softened.

Does leaking mean the dose has not absorbed?

Leaking after a progesterone suppository does not usually mean the dose has not absorbed.

Residue that appears later, after the suppository has softened, is different from a suppository that comes back out whole or nearly whole soon after insertion.

A softened suppository has already released progesterone from its base. The residue that appears later is usually the remaining softened base mixed with vaginal fluid.

A suppository that comes back out whole or nearly whole soon after insertion is different. In that situation, the question is whether it stayed in place long enough to soften and release progesterone.

Irritation, soreness and vaginal discomfort

Vaginal progesterone can cause local irritation because the medication is being used directly inside the vagina.

The tissue is exposed to the suppository, the softened base, residue, moisture and repeated insertion. Over several days, that can leave the vaginal opening and surrounding vulval skin feeling more sensitive.

Irritation may feel like stinging, burning, itching, rawness, tenderness, swelling, or a bruised feeling around the vaginal opening. The discomfort may be inside the vagina, on the vulval skin, or both.

Residue can add to the problem when it sits against the skin. Moisture on a liner can rub. Extra wiping can also make the area feel more sore, especially when the skin is already irritated.

Liners can help contain discharge, but they can become part of the irritation if they stay damp or rub against sensitive skin. Changing them when needed and patting rather than rubbing can reduce friction.

The aim is not to scrub away every trace of residue. It is to keep the area as comfortable as possible while you continue the medication as prescribed. Using the insertion method described in your product instructions can also make repeated use easier to manage.

Intercourse while using progesterone suppositories

Intercourse can feel different when progesterone is being used vaginally in a frozen embryo transfer cycle.

The suppository base softens after insertion and can leave residue or discharge. That residue may be present inside the vagina or around the vaginal opening. Repeated use can also make the vaginal tissue and surrounding vulval skin more sensitive.

That can change how sex feels.

It may feel messier than usual because of discharge or softened base. It may feel drier, more tender, stingy or irritating because the tissue has already been exposed to medication, residue, moisture, wiping, liners or repeated insertion.

Friction can make soreness more noticeable. If the vulval skin or vaginal opening is already irritated, intercourse may feel uncomfortable in a way that has nothing to do with desire or emotional connection. It is a physical effect of using medication in a sensitive area every day.

That physical change can matter emotionally too. In a FET cycle, intimacy is happening alongside medication timings, transfer instructions and the pressure of not wanting to get anything wrong. Residue, discharge or soreness can make sex feel less straightforward than it normally would.

If your clinic has given you specific instructions about sex before or after embryo transfer, follow those instructions for your own cycle.

Symptoms after transfer are hard to read

After embryo transfer, you will want to know whether implantation has happened as early as possible.

That is why every sensation can feel loaded with meaning. Cramping, bloating, breast tenderness, fatigue, headaches, nausea, discharge, spotting or mood changes can all feel significant because they arrive at the point when you are looking for signs from your body.

Progesterone is one reason those signs are difficult to read.

Vaginal progesterone can cause breast tenderness, bloating, headaches, tiredness, mood changes, nausea, discharge and local irritation. Those symptoms can overlap with the effects of oestrogen medication, the transfer procedure, normal pelvic sensitivity and early pregnancy changes.

This is why symptoms after transfer are not a reliable way to read implantation.

The same symptom can have more than one explanation. Cramping can feel hopeful one hour and worrying the next. Discharge can come from vaginal progesterone rather than implantation. Breast tenderness and fatigue can come from medication before a pregnancy test can give any clear answer.

The absence of symptoms can be just as unsettling. Implantation does not create one clear symptom pattern that every woman can feel or identify.

After transfer, symptoms can tell you what you are experiencing. They cannot confirm whether implantation has happened.

Your clinic’s pregnancy test is the point that gives clearer information.

When to contact your clinic

Progesterone suppositories can cause discharge, residue and local irritation. They can come from how vaginal progesterone is used: the suppository softens, leaves residue behind, and exposes sensitive tissue to repeated contact.

Some changes need clinic guidance because they are not ordinary suppository residue.

Bleeding is one of them. Light spotting can happen after embryo transfer, but bleeding still needs to be interpreted in the context of your transfer timing, medication plan and history.

Contact your clinic promptly if bleeding becomes heavier, bright red, painful, or comes with dizziness.

You should also contact your clinic if you have strong pelvic pain, fever, painful urination, discharge with a concerning smell, a rash, swelling, breathing symptoms, chest pain, visual changes, or a severe headache.

Medication issues need a different response from ordinary leakage. A missed dose, a dose used at the wrong time, a suppository that comes straight back out, or running short of progesterone are not the same as residue appearing after a suppository has softened.

Those situations cannot be judged from residue on a liner. They need your clinic’s guidance because they involve the medication plan itself, not ordinary leakage after a suppository has softened.

The limitations of progesterone suppositories

Progesterone suppositories do one specific medication job in a frozen embryo transfer cycle. They provide progesterone to help prepare and maintain the uterine lining for embryo implantation.

That is important, but it is not the full implantation process.

Implantation is wider than progesterone alone. It has 5 distinct phases and each has its own nutrient requirements.

Progesterone supports the lining environment for implantation. It does not cover the full nutritional and physiological demands of the implantation process.

The Now Baby FET Implantation Support Meal Plan is designed to support the next phase: targeted nutrition for the 5 stage implantation process after frozen embryo transfer.

Get the FET Implantation Support Meal Plan

PIO stands for progesterone in oil.

PIO provides progesterone support to help prepare and maintain the uterine lining according to your clinic’s FET protocol.

PIO shots can feel like one of the biggest parts of a frozen embryo transfer cycle before you ever reach transfer day. You may be thinking about the needle, the timing, the bruising, the soreness, and whether the injection has gone in the right place.

Why PIO shots are used before and after FET

PIO provides progesterone support to help prepare and maintain the uterine lining according to your clinic’s FET protocol.

Before transfer, progesterone helps bring the lining into the phase your clinic wants for embryo transfer. After transfer, progesterone support continues to help maintain the lining during the early post-transfer phase.

PIO shots are one route for giving that progesterone before and after FET.

PIO shots versus progesterone suppositories

PIO shots and progesterone suppositories are two different prescribed routes for progesterone support. PIO is injected into muscle, where progesterone in oil is absorbed into the bloodstream. Progesterone suppositories are placed vaginally.

You may have a clear preference. PIO can feel more daunting because it involves a needle, muscle soreness, and bruising. Suppositories can feel easier for some patients, but they can also feel messy, irritating, or harder to manage through the day.

In medicated FET cycles, one clinical trial found live birth rates of 44% with intramuscular progesterone, 46% with combined vaginal and intramuscular progesterone, and 27% with vaginal progesterone alone. This is why clinics may prescribe PIO even when suppositories look easier to manage.

How to minimize injection discomfort

PIO is given into muscle, so injection comfort depends on the site, muscle tension, and technique. PIO shots are often easier when you are not trying to twist, tense, and inject at the same time. Use the area your clinic showed you, and ask them to mark it again when you are unsure. The upper outer hip or buttock area is usually used because it keeps the injection away from the sciatic nerve.

To make PIO shots easier to tolerate:

• Warm the syringe in your hand before injecting, when your clinic allows this.
• Keep the muscle relaxed rather than tense.
• Ask your partner to do the injection when that feels easier, especially if twisting to reach the site makes the muscle tense.
• Inject slowly and steadily.
• Rotate sides so the same area is not used repeatedly.
• Avoid injecting into an area that is already bruised, hard, swollen, or very sore.
• Apply gentle pressure afterwards if there is bleeding.
• Use gentle movement after the injection to help the muscle loosen.
• Use heat after the injection when your clinic has said this is safe.

Pain, bruising, and lumps can happen with PIO, but the injections should still be manageable. Contact your clinic when the pain is severe, the area becomes hot or increasingly swollen, or the injections are becoming difficult to continue.

Common PIO symptoms and side effects

PIO symptoms can come from the injection site and from progesterone itself. Injection-site symptoms are usually local: tenderness, bruising, lumps, tightness, or soreness in the muscle. Progesterone medication can also cause symptoms through the rest of the body.

Common progesterone-related symptoms can include:

• Bloating: eat at regular intervals, avoid skipping meals, and choose simple, balanced portions when your digestion feels slower.
• Constipation: increase fluids, include fibre-rich foods, and keep gentle movement in your day when your clinic has not restricted activity.
• Breast tenderness: wear a supportive bra and avoid using this symptom as a sign of whether the transfer has worked.
• Tiredness or sleepiness: allow more rest where you can, especially when progesterone makes you feel heavy or slowed down.
• Mood changes: name it as a medication effect and reduce extra pressure where possible.
• Mild cramping or pelvic heaviness: note the symptom, but avoid reading it as proof of implantation or failure.

These symptoms can feel emotionally loaded after transfer, but they are common progesterone effects. Contact your clinic when symptoms are severe, unusual for you, or making it difficult to continue the medication as prescribed.

Why symptoms do not tell you whether implantation worked

PIO can cause symptoms that feel like early pregnancy because both are linked to progesterone. That overlap makes symptoms feel meaningful, but it does not make them diagnostic.

PIO-related symptoms that can overlap with early pregnancy include:

• Breast tenderness
• Bloating
• Tiredness or sleepiness
• Mild cramping
• Constipation
• Mood changes
• Pelvic heaviness
• Frequent urination

This is the part that matters after FET: progesterone can make your body feel pregnant before a pregnancy test can tell you whether implantation has happened. A strong symptom day does not confirm implantation, and a quiet symptom day does not mean anything has gone wrong.

When to call your clinic about PIO

PIO is prescribed as part of your FET protocol, so the first reason to call your clinic is anything that could affect the dose, timing, or delivery of progesterone. A late dose, missed dose, leaking medication, a bent needle, uncertainty about whether the full dose went in, or running low on supplies all need clinic guidance.

The second reason to call is when the injection site is no longer just sore. Bruising, tenderness, and small lumps can happen with PIO, but increasing heat, spreading redness, worsening swelling, severe pain, discharge, fever, or feeling unwell needs medical advice. These symptoms need to be checked because they can point to irritation, infection, or a reaction that should not be managed by guessing at home.

The third reason to call is when PIO is becoming difficult to continue. Severe injection anxiety, repeated painful lumps, difficulty reaching the correct site, or pain that makes you dread the next dose are valid reasons to ask for help. Your clinic may want to review your injection technique, confirm the site, check the prescription, or advise on the next step.

Keep taking PIO exactly as prescribed unless your clinic changes the prescription.

The limitations of PIO

PIO provides progesterone support to help prepare and maintain the uterine lining according to your clinic’s FET protocol. That is an important part of a frozen embryo transfer cycle, but progesterone is not the whole implantation process.

After transfer, your body is supporting several linked processes:

• A receptive lining — the endometrium needs to stay in the right phase for implantation.
• Early attachment — the embryo and uterine lining begin the first stages of contact.
• Blood flow support — oxygen and nutrients need to reach the implantation site.
• Immune balance — the immune system needs to support implantation without overreacting.
• Early placental signals — the first steps toward placental development and pregnancy signalling begin.

PIO supports the progesterone part of your FET protocol. Targeted nutrition supports the implantation needs progesterone does not cover.

The Now Baby FET Implantation Support meal plan takes all the guesswork and macro counting out of it for you.

Starting the day after transfer, it gives you a clear nutrition structure for the implantation window; balanced macros, targeted nutrient and meals designed to support successful implantation.

Your clinic manages the progesterone protocol. The Now Baby FET Implantation Support meal plan gives you the nutrition structure progesterone cannot provide: balanced macros, steady nourishment and clear daily meals from the day after transfer through the two-week wait.

FET Implantation Meal Plan

Your clinic maps your progesterone protocol.

The Now Baby FET Implantation Support meal plan maps your nutrition from the day after transfer through the implantation window.

With balanced macros, targeted nutrients and professionally developed daily meals for the implantation window, it takes all the guesswork out for you.

Get the FET Implantation Support Meal Plan

A euploid result from PGT-A testing is the best result you can hope for from this type of embryo screening. It means the trophectoderm cells biopsied from your embryo showed 46 chromosomes, which matters because embryos with missing or extra chromosomes are less likely to keep developing. The trophectoderm is the outer layer of the blastocyst, which later helps form the placenta. So when your report says euploid, it is giving you reassuring chromosome information from the cells that were tested.

What does aneuploid mean?

An aneuploid embryo has a chromosome number that is not 46. There may be an extra chromosome, a missing one, or both — across one pair or several.

Chromosomes carry the genetic instructions that guide every stage of development. When the number is wrong, those instructions are incomplete. The embryo may begin to divide, but in the vast majority of cases the development cannot continue. This is not a failure of the embryo in any other sense — not its appearance, not its development speed, not how it looked under the microscope. It is a chromosomal finding from the cells that were biopsied, and it is why aneuploid embryos are not recommended for transfer.

Aneuploidy is also more common than most women are told. In women aged 35–37 the aneuploidy rate across tested embryos is around 54% — rising to 63% at 38–40 and 66% at 41–42. PGT-A makes visible something that has always been happening. If your embryos came back aneuploid, that is a hard result to sit with. It is also the test doing exactly what it was designed to do. This is not a reflection of your body failing. It is the biology of human reproduction. PGT-A makes visible something that has always been happening. If your embryos came back aneuploid, that is a hard result to sit with. It is also the test doing exactly what it was designed to do.

What does mosaic mean?

Mosaic is between euploid and aneuploid. The biopsy detected a mixture of chromosomally normal and abnormal signals in the same sample.

It does not mean the embryo is aneuploid. What it means depends on two things: how much of the sample was abnormal, and which chromosomes were involved. Not all chromosomes carry the same clinical significance. Some chromosome abnormalities are associated with more serious developmental consequences than others — certain chromosomes, if affected, are incompatible with development regardless of the proportion involved, while abnormalities on others may carry less clinical weight. Your clinic will read your mosaic result against both of these factors before any transfer decision is made.

Some mosaic embryos have been transferred and resulted in healthy pregnancies. The evidence on mosaic transfer outcomes shows results vary considerably by mosaicism level and chromosome type. A mosaic result is not a closed door. It is a result that needs your specific details, not a general category.

What does no result or inconclusive mean?

An inconclusive result means the laboratory could not produce a clear classification from the biopsy taken. It does not mean the embryo is abnormal.

The biopsy removes a small number of trophectoderm cells — typically five to eight. That sample then goes through a process of DNA amplification before analysis. If the sample fails to amplify sufficiently, or produces signals that fall below the threshold required for a confident classification, the result comes back inconclusive. The embryo itself has not been assessed. The sample has. Those are not the same thing.

Receiving an inconclusive result after waiting for your PGT-A report is its own particular difficulty. It does not close a door — but it does not open one cleanly either. Your clinic may discuss rebiopsy if the embryo is still viable and the grade supports it. In some cases, transfer may be considered on the basis of the embryo’s other characteristics. An inconclusive result is a laboratory outcome. It is not a verdict on the embryo.

What does chaotic or complex abnormal mean?

These terms are not simply another word for aneuploid. They describe something more extensive.

An aneuploid result typically involves one chromosome pair — an extra copy, or a missing one. Chaotic and complex abnormal describe embryos where multiple chromosomes across multiple pairs are affected simultaneously. The disruption is not isolated. It is systemic. The chromosome picture has no coherent pattern from which development could reliably proceed.

Neither is recommended for transfer. If you see these terms on your report, they are telling you something specific about the scale of the chromosome disruption — not about you, not about your age, not about what is possible in a future cycle.

How do PGT-A results connect with embryo grading?

Your embryo grade and your PGT-A result are two separate assessments measuring different things.

Most clinics use the Gardner system. It grades a blastocyst across three criteria:

• Expansion (1–6) — how far the blastocyst has developed. 1–2 is early and limited. 3 is full. 4 is expanded. 5 is hatching. 6 is fully hatched.
• Inner cell mass (A–C) — the cells that later form the fetus. A is tightly packed and clearly defined. B is looser with moderate organisation. C is fewer cells with less defined structure.
• Trophectoderm (A–C) — the outer cells involved in implantation and placental formation. A is many cells forming a cohesive layer. B is fewer cells, less organised. C is sparse or irregular.

A 4AA describes an expanded blastocyst with strong organisation in both the inner cell mass and trophectoderm. A 3BB describes a slightly earlier stage with moderate cellular structure.

PGT-A tells you about chromosome number. A 4AA embryo can be aneuploid. A 3BB can be euploid.

Where both are read together is with mosaic embryos. Grade is one of the factors a clinic weighs when deciding whether a mosaic embryo is a transfer candidate — alongside mosaicism level and chromosome type.

Which result matters most before FET?

Your PGT-A result and your embryo grade are both part of your clinic’s picture. Neither replaces the other. The chromosome result tells your clinic which embryos are candidates for transfer. The grade tells them how those embryos developed and how to handle them.

If you have a euploid embryo moving toward transfer, the chromosome checkpoint has been passed. Your clinic has what it needs to proceed. The question you have been carrying — is this embryo ready — has been answered. What you are asking now is different.

Having a tested embryo for transfer is an important milestone, but is not your final destination.

The next question is: is my body ready?

After a euploid result, the focus changes

Research on single euploid blastocyst transfer puts live birth rates at around 62%. In reproductive medicine, that is a significant figure. It tells you something important: a chromosomally normal embryo, transferred into a prepared uterus, has real and meaningful odds.

It also tells you something else. There is a gap. And the gap is not about the embryo — your embryo has passed that screen. The gap is about everything that happens after transfer.

Implantation is not a single event. It is a biologically active phase — a precise window in which five distinct processes must unfold in sequence:

• Uterine lining — the endometrium must develop the structural conditions to receive the embryo. Adhesion molecules and signalling factors must be expressed at exactly the right moment.
• Early blood supply — new blood vessels must form rapidly to deliver oxygen and nutrients to the implantation site.
• Gene expression — cellular differentiation begins immediately. Methylation nutrients are essential at this stage. What is missing here cannot be corrected later.
• Placental formation — trophoblast embedding begins almost as soon as the embryo attaches. Nutrient transfer and hormonal signalling start here.
• Immune modulation — your immune system must shift into active tolerance, recognising the embryo while continuing to support vascular remodelling and embedding.

Each of those five processes has a specific nutritional demand. The fourteen days after transfer are when those demands are active. This is not a window where general healthy eating or supplements is enough.

The Now Baby FET Implantation Meal Plan is built around exactly that window. Every meal across the fourteen days has been designed around the nutritional demands of the implantation window — every process, every nutrient, every day — professionally analysed and structured so that the one variable that remains within your control is no longer left to chance.

You have optimised everything your clinic controls. This is the part only you can do.

Letrozole is widely associated with ovulation induction, so finding it on a frozen embryo transfer medication plan can seem unexpected. Your embryos have already been created and no eggs are being collected.

In an FET cycle, letrozole has a narrower job. Understanding that job explains why your clinic has chosen this route, what the additional medication is for and what letrozole can — and cannot — contribute to the transfer.

Why is letrozole used in a frozen embryo transfer cycle?

Before a frozen embryo can be transferred, the endometrium must develop and then receive progesterone for the correct length of time. A letrozole FET creates an ovulatory route to that transfer window.

This can provide an alternative to relying entirely on spontaneous ovulation or using a programmed cycle in which oestrogen and progesterone medication prepare the lining. The clinic can work with your ovarian response while monitoring the cycle closely enough to time the transfer.

Letrozole is being used to organise the cycle before transfer. It does not act on the frozen embryo.

How does letrozole prepare your body for embryo transfer?

Letrozole blocks aromatase, temporarily reducing oestrogen feedback so that follicle-stimulating hormone increases and encourages a follicle to develop.

As that follicle grows, your own oestrogen production rises and the endometrium develops. After ovulation, the follicle becomes the corpus luteum, which produces progesterone for the next phase of the cycle.

This distinction matters: letrozole does not build the lining by supplying oestrogen. It prompts the ovarian response that generates the hormones used in an ovulatory FET cycle. Your clinic then uses ovulation and progesterone exposure to align the endometrium with the developmental age of the embryo.

Who may be offered a letrozole FET cycle?

You may be offered letrozole if absent or irregular ovulation would make a natural FET difficult to begin or time. It is commonly considered for women with PCOS or long, irregular cycles.

Letrozole-assisted FET is also used in women who ovulate regularly. In that setting, it allows the clinic to create and monitor an ovulatory cycle rather than replacing it with a fully programmed protocol.

Your diagnosis does not decide the protocol on its own. Previous cycle response, endometrial development and the clinic’s approach to FET preparation also shape the recommendation.

What happens during a letrozole frozen embryo transfer cycle?

Letrozole is taken for a short course early in the menstrual cycle. Your clinic then uses ultrasound, and sometimes hormone tests, to follow the developing follicle and endometrium.

Once the follicle is ready, the clinic may wait for your natural luteinising hormone surge or give an hCG trigger to control when ovulation occurs. The transfer date is calculated from ovulation and any prescribed progesterone so that the endometrium reaches the correct stage for the developmental age of the embryo.

The exact tablet dose, monitoring schedule and transfer calculation vary between clinics. Follow the dates on your own treatment plan, particularly if the clinic changes them after a scan or blood test.

Why might you still need an hCG trigger or progesterone?

Each medicine has a separate job.

Letrozole supports follicle development but does not provide a precise ovulation time. An hCG trigger can give the clinic a defined point from which to schedule ovulation and transfer. If your natural hormone surge is clear and appropriately timed, a trigger may not be needed.

Because the trigger contains hCG — the hormone measured by pregnancy tests — testing before your clinic’s scheduled date may give a positive result from the injection rather than implantation. Letrozole itself does not cause a false-positive pregnancy test.

Progesterone may be prescribed after ovulation as luteal support. Its use does not mean letrozole has failed or that your body produced no progesterone. The clinic is adding support to the post-ovulation phase and controlling the progesterone exposure used to time transfer.

Does letrozole improve frozen embryo transfer success rates?

Letrozole can make an ovulatory FET cycle possible or easier to time. That is different from proving that the medicine itself makes implantation more likely.

Current evidence does not establish a higher live-birth rate with letrozole-assisted FET than with programmed endometrial preparation in women with PCOS.

The relevant measure is whether the protocol solves the problem it was selected for: creating a usable ovulation and giving the clinic a reliable transfer window. Embryo competence, accurate timing and the biology after transfer still determine whether pregnancy continues.

If your clinic recommends letrozole, ask what it is intended to achieve in your cycle. The answer should be more specific than improving your chance of success.

What are the side effects of letrozole during FET?

Letrozole is usually taken for only a few days. Possible effects during a short fertility course include hot flushes, headache, tiredness, dizziness and nausea.

More than one follicle can develop, which is one reason the ovaries are monitored during the cycle. Your clinic will tell you whether the response is appropriate for the planned transfer.

Preparing for implantation in a letrozole FET cycle

Letrozole helps your clinic establish the hormonal route to transfer. The trigger and progesterone refine its timing. Once the embryo has been transferred, implantation still has to unfold.

Implantation has 5 distinct phases and each has to complete successfully for pregnancy to continue.

The two-week wait is not a passive phase; it is biologically active. Each phase creates different nutritional and metabolic requirements as implantation progresses.

The Now Baby FET Implantation Support Meal Plan translates those changing requirements into 14 days of precisely structured, professionally measured nutrition. Every ingredient, quantity and meal is designed around the biological demands of the implantation process.

Your nutritional support for implantation is measured, planned and ready for when implantation is beginning.

Get the FET Implantation Support Meal Plan

You may have reached egg collection expecting the next step to be a fresh embryo transfer. Instead, you developed OHSS and your clinic cancelled the transfer. If an embryo implanted, the resulting rise in hCG could intensify the ovarian swelling and fluid shifts already caused by OHSS, allowing a manageable complication to become medically dangerous. Cancelling the fresh transfer removes that pregnancy-driven risk while your body recovers.

Egg collection, fertilisation and embryo development follow the same process whether the transfer is fresh or frozen. The difference now is instead of having a fresh transfer as part of this cycle, embryos that meet your clinic’s usual freezing criteria are frozen instead.

Once you have recovered and it is medically safe to proceed, transfer takes place in a separate frozen embryo transfer cycle. Your womb lining is prepared before an embryo is thawed and transferred.

Why Was Your Fresh Embryo Transfer Cancelled Due to OHSS?

OHSS develops when the ovaries respond excessively to the stimulation medicines used before egg collection. The ovaries become enlarged and release substances that make blood vessels more permeable, allowing fluid to leave the bloodstream and collect in the abdomen and, in more severe cases, around the lungs.

The hCG trigger used before egg collection can start this process. If a fresh embryo transfer resulted in pregnancy, the developing pregnancy would produce more hCG. This could intensify the ovarian swelling and fluid shifts, prolong the OHSS and increase the risk of serious complications including breathing difficulties, blood clots and reduced kidney function.

Pregnancies affected by OHSS are also associated with a higher risk of pre-eclampsia and premature birth. Cancelling the fresh transfer therefore protects both you and a potential pregnancy. It removes the risk of pregnancy continuing to drive the OHSS while your ovaries recover and your fluid balance returns to normal.

What Happens to Your Embryos After the Transfer Is Cancelled?

Cancelling your fresh transfer does not stop fertilisation or embryo development. Your embryology team continues to monitor the embryos in the laboratory, just as it would during a fresh-transfer cycle.

The difference comes when an embryo would usually be selected for transfer. Because no embryo can be placed into your womb while you have OHSS, the clinic freezes the embryos that meet its usual freezing criteria. These criteria apply to every embryo being considered for freezing.

The number frozen will depend on how many fertilised eggs continue developing and reach the stage and quality required by your laboratory. Your clinic should tell you how many embryos were frozen, the day each was frozen and its grade.

The embryos then remain in storage while you recover. They are not continuing to develop during this time: freezing pauses their biological activity until one is thawed for a later frozen embryo transfer.

What Happens to Your Body After Egg Collection and OHSS?

After egg collection, your ovaries remain enlarged and the blood vessels may continue leaking fluid into your abdomen. This can cause bloating, abdominal pain, nausea, rapid weight gain and reduced urine output. More severe fluid shifts can affect your breathing, circulation and kidney function.

Your clinic may monitor your weight, abdominal swelling, urine output, blood tests and symptoms. Treatment depends on the severity of the OHSS and may include fluids, medication to reduce the risk of blood clots, drainage of fluid from the abdomen or hospital care.

Without a pregnancy producing further hCG, OHSS usually begins to settle as the trigger medication leaves your body. Your ovaries gradually reduce in size, the fluid moves back into the bloodstream and your kidneys remove it through urine. A cancelled transfer reduces the risk of OHSS being prolonged by pregnancy, but you still need monitoring until the complication has resolved.

When Can You Have a Frozen Embryo Transfer After OHSS?

Your frozen embryo transfer will not be scheduled until the OHSS has resolved and your ovaries and fluid balance have returned to baseline. This usually means allowing the egg-collection cycle to end and waiting for at least one period before beginning an FET cycle.

The exact timing depends on the severity of the OHSS, how quickly your body recovers and the type of frozen transfer cycle your clinic recommends. Mild OHSS may settle within a couple of weeks, while more severe OHSS can delay treatment for longer.

Waiting does not change the time your embryos spend developing. Once frozen, their biological activity is paused until an embryo is thawed for transfer. The delay allows the effects of ovarian stimulation to settle so the transfer can take place in a separate cycle prepared for implantation.

Does a Freeze-All Cycle Affect Your Chance of Success?

Your chance of a live birth from this egg collection is best assessed across all the embryos transferred from it. This is the cumulative live birth rate, rather than the outcome of the first transfer alone.

Research comparing freeze-all cycles with cycles that begin with a fresh transfer has found little or no difference in cumulative live birth rates. The embryos are transferred later, after your body has recovered from ovarian stimulation and OHSS.

The frozen pathway introduces a freezing and thawing stage before transfer. Your individual outcome therefore depends on how many embryos are frozen, whether an embryo survives thawing and what happens during each frozen embryo transfer. The change from fresh to frozen primarily changes the timing and process, rather than lowering the overall chance from the egg collection.

Supporting Implantation After Your Frozen Embryo Transfer

OHSS changed your route from egg collection to embryo transfer. Once you have recovered and your frozen transfer goes ahead, the focus moves firmly towards what happens next.

Embryo transfer is the clinical procedure. Implantation is the biological process that must follow.

Implantation has 5 distinct phases and each has to complete successfully for pregnancy to continue.

The two-week wait is not a passive phase; it is biologically active. Each phase creates different nutritional and metabolic requirements as implantation progresses.

The Now Baby FET Implantation Support Meal Plan translates those changing requirements into 14 days of precisely structured, professionally measured nutrition. Every ingredient, quantity and meal is designed around the biological demands of the implantation process.

Your nutritional support for implantation is measured, planned and ready for when implantation is beginning.

Get the FET Implantation Support Meal Plan

You can look at one IVF success rate and see a low percentage per egg collected, then look at another and see a much higher percentage per embryo transfer. It can feel as though one of them must be wrong.

Usually, neither is.

Each percentage starts counting at a different point. A live birth rate per egg retrieved begins with every egg collected. A live birth rate per egg collection looks at the whole collection procedure. A live birth rate per embryo transfer begins later, once an embryo has already reached transfer.

That difference matters because an egg still has to fertilise, develop and become suitable for transfer before pregnancy can begin. A percentage measured from embryo transfer leaves those earlier stages outside the calculation.

Once you can see where each percentage begins, the figures stop contradicting each other. They start answering different questions.

The three IVF success rates are measuring different things

A live birth rate per egg retrieved starts with each individual egg collected. It follows that egg through fertilisation, embryo development, transfer, implantation and pregnancy.

A live birth rate per egg collection starts with the retrieval procedure as a whole. It looks at whether that collection eventually led to a live birth, sometimes including more than one embryo transfer from the same group of eggs.

A live birth rate per embryo transfer starts much later. It includes only embryos that developed far enough to be transferred.

This is why the percentage per embryo transfer is usually higher. It begins after several earlier stages have already been completed. The percentage per egg retrieved begins before any of them have happened.

What live birth rate per egg retrieved means

A live birth rate per egg retrieved starts with every egg collected during retrieval.

It then follows each egg through every stage that comes after: fertilisation, embryo development, transfer, implantation and pregnancy.

That is why this percentage is much lower than the live birth rate per embryo transfer. It includes eggs that do not fertilise, embryos that stop developing and embryos that never reach transfer.

The figure also changes with age. A percentage that may be reasonable for one age group can be far too high for another.

So an average of around 8% per egg retrieved may be useful in a worked example, but it should not be read as your personal chance from each egg.

What live birth rate per egg collection means

A live birth rate per egg collection starts with the retrieval procedure, rather than with each individual egg.

It asks whether that collection led to a live birth.

The important detail is whether the figure includes only the first embryo transfer or all fresh and frozen transfers created from that collection.

When all transfers are included, the result is a cumulative live birth rate per egg collection. This gives a fuller picture of what one retrieval produced overall.

So before comparing clinic figures, check whether the percentage is based on the first transfer only or on every transfer from the same collection. They are not measuring the same thing.

What live birth rate per embryo transfer means

A live birth rate per embryo transfer starts with the embryo placed in the uterus.

It does not include the eggs that did not fertilise or the embryos that did not develop far enough to be transferred.

That is why this percentage is higher than the live birth rate per egg retrieved. It begins later, after several earlier stages have already been completed.

It can be useful when you want to know what happened once an embryo reached transfer. It cannot tell you what one egg collection produced overall.

One egg collection can produce three different success rates

Take one simplified example:

• 8% live birth rate per egg retrieved
• 40% cumulative live birth rate per egg collection
• 30% live birth rate per embryo transfer

These percentages are describing the same IVF pathway from different starting points.

The 8% begins with every egg retrieved.

The 30% begins only when an embryo reaches transfer.

The 40% looks at the egg collection as a whole and includes the chance of a live birth across all the embryos transferred from it.

That percentage can be higher than the rate per embryo transfer because one egg collection may produce more than one opportunity for transfer.

The figures have not changed because the treatment became more or less successful. The percentage changes because the starting point changes.

After a failed first transfer, it can feel as though the odds have already moved against you.

They have not automatically changed because this is your second attempt.

Here, a failed transfer means that the pregnancy test was negative. A biochemical pregnancy or miscarriage confirms that implantation began and needs to be understood as pregnancy loss rather than failed implantation.

In 2023 UK data, the average live birth rate was 33% per frozen embryo transferred. Approximately two out of every three frozen embryo transfers did not result in a live birth.

Your first result belongs within that wider reality. The chance attached to your next FET will depend on the embryo being transferred and the conditions in which it attempts to implant.

Does One Failed Embryo Transfer Reduce Your Chances Next Time?

One negative pregnancy test cannot establish why the transfer did not work.

If the embryo was untested, a chromosome error may have prevented development from continuing. A highly graded embryo can still have a chromosome error because grading assesses appearance and developmental progress, not chromosome number.

A euploid PGT-A result reduces that particular uncertainty, but euploid embryos do not produce a live birth after every transfer. Chromosome screening cannot assess every part of embryo development or complete implantation on the embryo’s behalf.

After transfer, the embryo must continue developing while communicating with the uterine lining. Attachment, invasion, changes to the maternal blood supply, immune adaptation and early placental formation must follow in sequence.

A negative pregnancy test cannot show whether the embryo did not attach or whether development stopped before hCG reached a detectable level.

The transfer result tells you what happened. It does not tell you why.

Second Embryo Transfer Success Rates

Published second-transfer rates are difficult to compare because “second transfer” does not always describe the same treatment stage.

If your first transfer was fresh and your next will be frozen, this is your second embryo transfer overall but your first FET. Research reporting outcomes for a second FET may be describing a woman who has already had one fresh transfer and one frozen transfer.

Studies also measure different outcomes. A positive pregnancy test, clinical pregnancy, ongoing pregnancy and live birth are not interchangeable measures of success.

A 2024 study followed fresh transfers and subsequent frozen transfers using embryos from the same egg-collection cohort. The predicted positive pregnancy rates were:

• 32.8% for the first FET
• 30.8% for the second FET
• 28.9% for the third FET
• 27.1% for the fourth FET

These were positive pregnancy-test rates rather than live-birth rates. The study also involved a specific group of women and embryos, so the percentages cannot predict your result.

What they show is that meaningful pregnancy rates continued across later transfers. The chance reduced gradually rather than disappearing after the first FET.

Your clinic’s live-birth rate for embryos comparable with yours will give you a more relevant estimate. Ask whether its figure matches your embryo stage, PGT-A status, age at egg collection and intended FET protocol.

Why Success Rates Can Change Across Subsequent Transfers

Clinics usually transfer the embryo with the strongest stage and grade first.

If that transfer does not result in pregnancy, the next embryo may have a lower grade or may have reached the blastocyst stage later. The difference between first and subsequent transfer rates can therefore reflect differences between the embryos available.

Grading still cannot determine the fate of an individual embryo. Lower-graded embryos can result in live births, while highly graded embryos can produce negative pregnancy tests.

Does It Matter Whether Your First Transfer Was Fresh or Frozen?

A fresh transfer takes place within the stimulated egg-collection cycle. The ovaries have produced higher hormone concentrations, and the endometrium has developed within that hormonal environment.

A frozen embryo transfer takes place in a later cycle. The lining may be prepared through your own ovulation or with prescribed oestrogen and progesterone.

Moving to FET separates the next transfer from ovarian stimulation. This may be clinically useful, but it does not make every frozen transfer more successful than every fresh transfer. The embryo, reason for freezing and method of preparing the lining still matter.

In the 2024 same-cohort study, a negative pregnancy test after fresh transfer did not predict the result of the next frozen transfer.

For a woman moving from a failed fresh transfer to FET, that is the relevant finding: the fresh result did not establish the outcome of the remaining frozen embryos.

What Your First Transfer Can Tell Your Clinic

Your first transfer may provide information that helps your clinic plan the next one.

The review should cover:

• The stage, grade and PGT-A status of the embryo transferred
• Endometrial thickness and appearance
• Progesterone timing, dose and route
• Any progesterone blood result used by your clinic
• Missed, delayed or uncertain medication doses
• Whether the procedure was straightforward or technically difficult
• Catheter placement, blood, mucus or a retained embryo
• Previous findings involving the uterine cavity

A difficult procedure may change how the next transfer is planned. A medication or progesterone issue may justify an adjustment. A uterine-cavity concern may need further assessment.

Where the lining, medication and procedure progressed as intended, there may be no clinical reason to redesign the protocol.

A change is useful when it answers something found in the first cycle. Changing the plan simply because the result was negative can create more intervention without resolving the source of failure.

Do You Need More Tests After One Failed Embryo Transfer?

One failed transfer does not automatically justify extensive testing.

Further assessment may be appropriate when the first cycle revealed a specific concern, such as a difficult procedure, persistent lining difficulty, unexpected bleeding or a suspected uterine-cavity finding.

ERA, EMMA, ALICE, immune testing, natural killer cell testing and clotting panels are frequently offered after unsuccessful transfers. Current evidence does not support routine use after one failed transfer, and finding a difference on a test does not necessarily lead to an intervention proven to increase live birth.

The HFEA add-on reviews examine the evidence for these tests individually. They can help you separate an investigation prompted by your medical history from an add-on offered because the transfer was unsuccessful.

When More Than One Failed Transfer Changes the Clinical Picture

Repeated failure carries more weight when the embryos transferred had a higher expected chance of implantation.

Three failed euploid blastocyst transfers provide different clinical information from three failed transfers involving untested embryos. Age at egg collection, embryo stage and grading also affect what can be concluded from the number of attempts.

Current professional guidance therefore considers the expected implantation potential already transferred rather than relying on one fixed number of failures for every woman.

Once enough embryos with meaningful expected potential have been transferred without detectable implantation, a broader clinical review becomes more reasonable.

Per-Transfer and Cumulative Success Rates Measure Different Things

A per-transfer live-birth rate describes the outcome of one embryo transfer.

A cumulative live-birth rate describes the chance of at least one live birth after several transfers, or after all suitable embryos from one egg collection have been used.

The per-transfer rate is more relevant to the FET you are planning now. The cumulative rate helps explain what a group of stored embryos may offer over time.

In the 2024 same-cohort study, cumulative live birth reached 57% after the fresh transfer and up to three subsequent FETs. No individual transfer carried a 57% live-birth rate. The figure came from several opportunities combined.

This is why clinic statistics may look substantially higher when reported per egg collection rather than per embryo transferred.

Before using a published figure, check whether it measures:

• Pregnancy or live birth
• One transfer or several
• One embryo or an entire embryo cohort
• Fresh, frozen or combined treatment
• Untested or PGT-A-tested embryos

The number only becomes useful once you know what outcome and treatment period it represents.

What Will Shape the Success Rate of Your Next FET?

The embryo being transferred carries its own developmental potential.

Its age-related chromosome risk is linked to your age when the egg was collected. Its stage, grade, day of blastocyst development and PGT-A status provide further information, although none can determine the outcome alone.

The next FET must then establish the clinical conditions in which that embryo will attempt to implant:

• The uterine cavity
• Endometrial development
• Progesterone timing and exposure
• Embryo survival and development after warming
• The transfer procedure

These factors bring the embryo and endometrium to the point of transfer.

A success rate can estimate what may happen next. The implantation phase determines what happens next.

Supporting Implantation After Your Next Transfer

Implantation has 5 distinct phases and each has to complete successfully for pregnancy to continue.

Each phase has its own nutritional requirements.

Rapid cell division requires energy and the raw materials needed to copy DNA, build proteins and form cell membranes. Amino acids contribute to new tissue. Fatty acids are used in cell membranes and cellular communication. Vitamins and minerals participate in DNA synthesis, methylation, antioxidant defence, immune adaptation and early vascular development.

Metabolic stability matters because these processes need a consistent supply of energy and nutrients while implantation progresses. Supplements cannot offer this level of support.

Your clinic manages the embryo transfer with Precision. You should do the same with your nutrition for this critical phase.

The Now Baby FET Implantation Support Meal Plan has taken all of the guesswork out for you. The nutrients needed for the full implantation phase have been professionally curated into a plan that is easily implemented.

Get the FET Implantation Support Meal Plan.