Nutrition before pregnancy: how to support fertility

Can food improve fertility?

It does not ensure a pregnancy or resolve a medical cause of infertility, but it helps you start trying in better health. Infertility is usually described when pregnancy does not happen after twelve months of regular unprotected sexual intercourse [2]. If you are 35 or older, it is advisable to seek advice at six months [2].

There may be anatomical, hormonal, genetic or semen-related causes behind it, which are investigated in medical consultation and sometimes need assisted reproduction.

What we know about food is more modest than the market promises. According to the American Society for Reproductive Medicine, there is no solid evidence that a specific diet improves fertility in women who ovulate normally [2]. It does recommend a healthy diet and habits for both, because of their effect on general health [2].

The narrative review of diet and fertility describes patterns with vegetables, fruit, wholegrain cereals, fish and poultry [6]. It helps to understand the dietary context, but it does not set out a pattern that guarantees reproductive results [2].

How does weight affect fertility?

When looking at weight and fertility, weight is one part of the assessment, not a single requirement. Obesity may be associated with changes in ovulation and with risks during pregnancy, but body mass index alone does not explain a person’s fertility [7].

If you are considering assisted reproduction, you do not need to delay it automatically in order to reach a number on the scales. According to the ASRM, trials of weight loss before IVF in women who ovulate have not been shown to improve live births [7].

In women with obesity and anovulation, an individual intervention may help ovulation and conception without treatment, but it has not been shown to increase live births [7]. The team assesses with you your age, time trying, health and the safety of the procedure.

Why start folic acid before pregnancy?

The maternal nutrition guideline recommends starting folic acid before trying for a baby, ideally three months before, and continuing it for at least the first twelve weeks [1]. Check the details and the dose in the specific folic acid guide. Folates from vegetables and pulses help, but they do not replace this regimen.

If you are already trying to conceive or are in a cycle of assisted reproduction, do not wait to change your weight or diet before discussing the supplement with your midwife or doctor.

If you had a previous pregnancy affected by a neural tube defect, certain illnesses or medicines may call for a different dose under medical advice; do not calculate it from a multivitamin, and do not change your medication on your own. The specific regimen is explained in the folic acid guide [1].

Which foods and nutrients should be prioritised before pregnancy?

A varied pattern with vegetables, fruit, pulses, wholegrain cereals, fish and olive oil can help you look after your health before pregnancy. Fertility studies are mostly observational and do not show that a specific diet guarantees conception [2] [6]. Within that pattern, four groups deserve attention.

• Unsaturated fats and oily fish. Olive oil and fish can be part of a varied pattern. Studies on diet and omega-3 include associations and intermediate markers, such as seminal parameters. These data do not in themselves demonstrate an improvement in pregnancy or live birth, nor do they allow omega-3 supplements on their own to be recommended as a fertility treatment [2] [6].
• Plant protein. In a large study of American nurses, giving more weight to plant protein than to animal protein was associated with less infertility due to lack of ovulation [2] [6]. Pulses and tofu count here.
• Wholegrain cereals and pulses. They provide fibre and variety; if you have insulin resistance, the plan is adapted to your clinical situation.
• Iron and iodine. Iron comes from meat, fish, pulses and leafy greens. For iodine, dairy, fish and iodised salt, as recommended in preconception consultation [3].

The AESAN advises avoiding swordfish, bluefin tuna, shark and pike when planning a pregnancy, because of mercury [5]. This precaution protects the possible baby, without attributing to it any improvement in fertility.

If you have polycystic ovary syndrome

If you have a diagnosis of PCOS and are trying for a baby, agree with the fertility team how to combine your medical follow-up with food. An irregular period needs assessment: a dietary plan alone cannot establish its cause.

In women with obesity and lack of ovulation, weight management may help ovulation, but it has not been shown to increase live births [7]. This does not set a weight target for everyone with PCOS, nor does it replace their treatment.

You can take to the consultation your meal times and the restrictions you already follow. Reviewing what you eat helps to spot cuts that are hard to maintain, without looking for a “fertility diet” that promises a pregnancy [2].

And if you have low weight or irregular periods?

If your BMI is below 18.5 and your periods are irregular or absent, NICE indicates that gaining weight is likely to improve your chances of conceiving [4]. It is worth investigating the cause and agreeing the plan with the team; do not assume that any absence of periods is explained by weight alone.

Are supplements needed to improve fertility?

Beyond folic acid, check with your midwife or doctor whether you need iodine during pregnancy or breastfeeding [3]. If you follow a vegan diet, make sure you have an appropriate vitamin B12 plan. During pregnancy and breastfeeding, the AESAN recommends avoiding seaweed because its iodine content varies [8].

Do not start several complexes or extracts “for fertility” on your own.

The SEGO does not systematically recommend vitamin A supplements during pregnancy [3]. Discuss any supplement and medicine with the team looking after you: indications depend on your situation, and a product does not replace adequate food.

What changes if you are having assisted reproduction?

Food during assisted reproduction can help you meet your needs with a routine you can sustain. No diet, food or supplement guarantees implantation, pregnancy or birth; the evidence on dietary patterns and assisted reproduction results is mostly observational and does not allow any effect to be promised [2] [6].

Before adding products “for fertility” or making a dietary restriction, share with the team the supplements, drugs and weight changes you are considering.

The decision to start or postpone a cycle is taken with the fertility team according to your situation; it is not derived from a weight figure alone [7]. NICE refers folic acid supplementation to its maternal nutrition guideline and recommends reviewing medicines that may affect fertility or pregnancy [4].

How do smoking, alcohol and coffee affect fertility?

Habits of both partners count. Women who smoke have a higher risk of infertility and reach menopause between one and four years earlier [2]. This suggests that follicles are used up more quickly [2]. In men who smoke, changes in semen have been seen, although their effect on fertility is less clear [2].

Quitting smoking is the recommendation for both.

When trying for a baby, the ASRM notes that the evidence of harm to fertility from moderate drinking is limited [2]. NICE advises that the safest option to protect a possible embryo is not to drink alcohol while you are trying to conceive [4]. During pregnancy, avoid alcohol [4].

In men, high consumption impairs semen quality [4].

One or two cups of coffee a day do not appear to affect fertility [2]. During pregnancy, the EFSA considers that up to 200 mg daily of caffeine from all sources does not raise concern for the foetus [9]. If the stress of trying becomes hard to manage, asking for psychological support can also help.

What mistakes do we see in consultation?

• Waiting for the positive test to start folic acid. The regimen is recommended before conception [1].
• Putting all the attention on the woman. The weight, smoking and alcohol of the man also count, and it is worth reviewing the habits of both [2].
• Taking several “fertility” complexes at the same time. They often repeat the same vitamins, and you can lose track of what each product contains.
• Postponing trying until reaching an “ideal weight”. Age and time spent trying also count; decide with the team whether a change in weight adds anything in your case.
• Turning every meal into an exam. What counts is the whole week, and checking each plate only adds pressure to a stage that already has enough.

To review the habits of both, you can consult food and fertility as a couple. If the question centres on the man, there is the guide on male fertility and food.