5 Ways Hormonal Birth Control Affects Fertility

As a teenager growing up in Catholic Ireland in the seventies, contraception – and certainly “the pill” – was not an option. Condoms were only accessed by train trips to Northern Ireland where they were easily available. Even when the pill became available by prescription, it was only for married women.

We have come a long way since then in terms of our attitude to sexuality and our relationship with the church.

Imagine for a minute how different the world would be if the pill never became an option. The pill has changed the way that women think about the consequences of sex. It has allowed many of us to develop our potential to a much greater extent.

Being able to have sex without having to worry about rushing into marriage or parenthood has allowed women to focus on education and building careers before starting families. For the first time in history, the pill has allowed women to plan. So yes, on the face of it, the pill has been a liberator.

Beyond contraception, the pill is now prescribed for “period regulation,” for stopping periods for social reasons, and even for managing acne. The pill has brought many benefits, but it does come with a cost to our health. In this article, I want to look at five ways hormonal birth control affects fertility – especially when you are coming off it to try for a baby.

If you’ve recently stopped hormonal contraception and your cycle feels unsettled or slower to return than you expected, it doesn’t necessarily mean anything is “wrong.” These are often the physiological shifts that occur when your body begins reconnecting the natural hormone rhythms that were suppressed. The five effects below help to explain what is happening beneath the surface – and why the transition can take time.

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1. How the pill works: suppressing ovulation

Most combined oral contraceptive pills work by suppressing ovulation.

When ovulation is paused, your body’s natural hormone rhythm is also suppressed, and this is why your cycle can take time to settle once the pill is stopped.

During the 21 days of active pills, synthetic oestrogen and progesterone are taken every day. These synthetic hormones prevent the normal hormonal ups and downs that would usually lead to an egg being released. During the 7-day break, a bleed happens – but this is not the same as a natural period (more on that below).

Over time, this suppression can affect the usual communication between the brain, the pituitary gland, and the ovaries. When you stop taking the pill, your body has to “switch back on” this natural conversation, and that re-start does not always happen immediately.

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2. The pill doesn’t regulate your cycle

The bleed experienced during the 7-day break from the pill is not a true period; it is a withdrawal bleed in response to stopping synthetic hormones.

So when someone experiences a “regular cycle” while on the pill, this is not due to their own hormonal rhythm. It is a pharmaceutical-induced response.

When patients experience missing, heavy, or irregular periods, they are often prescribed the pill as a way to “regulate” or “balance” hormones. In reality, the pill does neither of these things. It prevents ovulation, which is the source of your own progesterone. A better way to describe the pill’s function is that it suppresses hormones rather than balances them.

Any hormone imbalance that led to the pill being prescribed in the first place has not been addressed. It will still be present when the medication is stopped – which is often when women notice that the original problem has never really gone away.

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3. The pill does not preserve egg count

Being on the pill for a long time, it can be easy to assume that the eggs you “didn’t use” while on it are somehow stored or preserved.

Unfortunately, this is not the case. Follicles containing your eggs continue to be recruited and brought forward for maturation and ovulation. The pill prevents the final ovulation step, so these follicles are not ovulated – but they are still lost.

Your egg reserve continues to diminish at its normal rate while you are taking the pill. The pill does not “save” eggs for later life; it simply stops those eggs from being released.

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4. How hormonal birth control affects gut health

Synthetic oestrogen can affect gut permeability and the balance of bacteria in the gut. About 70% of our immune system is located in the gut, so it is not surprising that the pill can be linked with recurrent issues such as:

• Yeast infections (thrush)
• Urinary tract infections (UTIs)
• Bloating or digestive discomfort
• More intense PMS or hormonal fluctuations after stopping the pill

Gut flora are involved in hormone regulation and oestrogen metabolism. When the gut is under pressure, it can make hormonal issues worse when coming off the pill, as the body tries to re-establish a healthy balance.

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5. The pill can deplete vital fertility nutrients

The mechanisms by which the pill affects specific vitamins and minerals vary, but research shows that long-term use can reduce levels of several key nutrients that are important for fertility, hormone balance, and early pregnancy.

Folate (especially methylated folate)
Folate is a water-soluble B vitamin essential for DNA synthesis, cell division, and methylation. The pill can negatively impact folate status through malabsorption, increased excretion, and faster metabolism of folate. This matters because optimal folate status is crucial before and during early pregnancy.

Riboflavin (B2)
B2 is involved in energy production and normal cell function and growth. Studies have shown a higher prevalence of riboflavin deficiency in women taking the pill, due to reduced absorption.

Vitamin B6
B6 participates in protein, carbohydrate and lipid metabolism, and in the biosynthesis of neurotransmitters (for example, converting tryptophan to niacin and serotonin). One large study found that plasma B6 concentrations were significantly reduced in most women taking the pill who did not use dietary supplements.

Vitamin B12
B12 is essential for cell metabolism, DNA synthesis and regulation, fatty acid synthesis, and energy production. Several studies have found lower B12 levels in women using the pill compared to non-users.

Vitamin C
Vitamin C is a cofactor in various metabolic processes, including collagen synthesis, and acts as an antioxidant. Pill use may reduce vitamin C levels, which can affect antioxidant protection.

Vitamin E
Vitamin E is a potent antioxidant that protects tissues from oxidative stress and free radicals. Studies have found decreased plasma vitamin E in pill users, suggesting less antioxidant protection and a possible increased risk of cardiovascular issues.

Zinc
Zinc plays roles in RNA and DNA metabolism, cell signalling, gene expression, and regulation of cell death. Zinc status is often lower in women using the pill.

Selenium
Selenium is a micronutrient that functions as a cofactor for antioxidant enzymes and plays a key role in thyroid function. The pill may interfere with selenium absorption, which can increase the risk of deficiency and put additional pressure on thyroid health.

Magnesium
Magnesium is required for more than 300 enzyme reactions in the body and must be bound to ATP to be biologically active. Inadequate intake or absorption can lead to deficiency, which may increase the risk of chronic disease and affect blood vessel function and blood coagulability. The pill may contribute to lower magnesium levels over time.

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Does hormonal birth control delay time to pregnancy?

A large study of over 116,000 women in the US found that use of the pill was associated with a delay in time to pregnancy after discontinuation. The length of this delay depended, in part, on the oestrogen dose in the pill.

This does not mean the pill causes infertility. What it does suggest is that your body may need some time to recover ovulation, rebuild nutrient stores, and re-establish healthy hormone rhythms when you stop taking it.

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Optimising your fertility after hormonal birth control

I am a firm believer that there is a solution to every problem. As Clinical Lead at Now Baby, my role is to help you understand what your body needs so you can move forward with clarity and confidence.

Because hormonal contraception can influence nutrient status and hormone signalling, recovery is often about restoring what has been depleted and supporting the body as ovulation re-establishes. In practice, that means prioritising bioavailable, comprehensive nutritional support before trying to layer on anything more complex.

NHP Advanced Female Fertility Support – comprehensive support when you’re coming off the pill

Long-term oral contraceptive use has been associated with reduced levels of key nutrients including folate, B-vitamins, zinc and magnesium. These nutrients are central to ovulation, hormone metabolism and early pregnancy development.

NHP Advanced Female Fertility Support is a practitioner-grade formula designed to provide structured nutritional support for women preparing for pregnancy.

It includes:

• Methylated folate (5-MTHF) to support optimal folate status before and during early pregnancy

• Active B-vitamins to support energy metabolism and hormonal balance

• Zinc, which contributes to normal fertility and reproduction

• Vitamin D, which contributes to the normal function of the immune system

• A broad spectrum of supportive nutrients to help restore nutritional reserves

This formula is suitable for women preparing for pregnancy, particularly after long-term hormonal contraceptive use where nutrient stores may require rebuilding.

You can order NHP Advanced Female Fertility Support directly from the Now Baby shop, with 20% off your first order.