Fertility and Preconception Health: Nutrition and Lifestyle Factors

The months before conception shape the health of a pregnancy and a child in ways that were underappreciated for decades. Many key developmental events, including closure of the neural tube, happen in the first weeks after conception, often before a pregnancy is recognised. Sperm take around 2 to 3 months to develop. And many conditions that affect pregnancy, from diabetes to thyroid disease to medicine use, are best addressed before conception rather than after. Preconception care is therefore one of the most valuable preventive opportunities in medicine, and one in which nutrition and lifestyle have a central role for both partners.

Nutrition for the person planning pregnancy

Folic acid

Folic acid taken before conception and in early pregnancy substantially reduces the risk of neural tube defects. Most guidelines recommend 400 micrograms daily from at least one month before conception until 12 weeks of pregnancy. A higher dose, often 5 milligrams, is recommended for women at increased risk, such as those with a previous affected pregnancy, diabetes, obesity in some guidelines, certain antiepileptic medicines or malabsorption, as advised by their doctor. Folic acid is effective regardless of MTHFR genotype.

Iodine

Iodine requirements increase in pregnancy, and deficiency, even mild, may affect the child’s neurological development. Many guidelines recommend an iodine containing supplement during preconception, pregnancy and breastfeeding, particularly where diets are low in dairy, fish or iodised salt. Kelp and seaweed supplements should be avoided because of variable and sometimes excessive iodine content.

Vitamin D

Supplementation is recommended in pregnancy by many guidelines, particularly for women with limited sun exposure or darker skin at higher latitudes.

Iron

Iron stores before pregnancy matter because requirements rise sharply. Checking and correcting iron deficiency before conception is sensible, particularly in women with heavy periods or vegetarian diets.

Vitamin B12

Important for women following vegan diets, those with gut disease or bariatric surgery and those taking metformin.

Omega 3

Adequate DHA intake, from fish low in mercury or algal supplements, reduces the risk of preterm birth.

Things to avoid

High dose vitamin A supplements, including cod liver oil, and liver in large amounts, because excess vitamin A can cause birth defects. Unregulated herbal products.

Weight and metabolic health

Both obesity and underweight reduce fertility and increase pregnancy risks. Obesity is associated with ovulatory dysfunction, gestational diabetes, pre eclampsia and birth complications; modest weight loss before conception can improve ovulation. Very low body weight and excessive exercise with low energy intake can suppress ovulation. The goal is a healthier weight through sustainable changes, avoiding restrictive diets in the months before conception that could compromise nutritional status.

Lifestyle factors

Medical conditions and medicines

• Diabetes: good glucose control before conception reduces the risk of congenital anomalies and miscarriage. Women with diabetes need specialist preconception care.
• Thyroid disease: thyroid hormone requirements rise in early pregnancy, and treatment usually needs adjustment as soon as pregnancy is confirmed.
• Polycystic ovary syndrome: assessment of glucose tolerance and support for ovulation.
• Hypertension, epilepsy, mental health conditions and autoimmune diseases: require review, as some medicines need changing before conception.
• Medicines with known risks in pregnancy include sodium valproate, isotretinoin, methotrexate, some antihypertensives such as ACE inhibitors, warfarin and statins. These should never be stopped abruptly without medical advice, but plans should be made before conception.

Vaccination and infections

Immunity to rubella and varicella should be confirmed before pregnancy, as these vaccines cannot be given during it. Screening for sexually transmitted infections and, where relevant, other infections is part of preconception care.

Male preconception health

Male factors contribute, alone or in combination, to around half of couples’ infertility. Sperm quality is affected by:

• smoking, heavy alcohol use and recreational drugs;
• obesity and metabolic disease;
• anabolic steroids and testosterone treatment, which can suppress sperm production profoundly;
• heat exposure, such as frequent hot baths or prolonged laptop use on the lap;
• some medicines and occupational exposures;
• varicocele and infections.

Antioxidant and micronutrient supplements are widely marketed for male fertility. A large randomised trial found that folic acid and zinc supplementation in men did not improve semen quality or live birth rates. Improving overall health, stopping smoking, reaching a healthier weight and avoiding testosterone are more reliable steps.

Age and timing

Female fertility declines with age, more steeply from the mid thirties, and the risk of miscarriage and chromosomal abnormalities rises. Male fertility also declines with age, though more gradually. Understanding the fertile window helps: conception is most likely from intercourse in the 6 days ending on the day of ovulation, with the highest probability in the 2 days before ovulation. Regular intercourse every 2 to 3 days covers this window without the stress of precise timing. Couples who have not conceived after 12 months of regular intercourse, or after 6 months if the woman is 35 or older, should seek assessment, sooner if there are known risk factors.

Diet patterns and fertility

Observational studies have associated dietary patterns rich in vegetables, whole grains, plant proteins, fish and unsaturated fats with better fertility outcomes in women, and patterns high in processed foods and sugar sweetened drinks with poorer outcomes. These are associations rather than proof, but they align with general recommendations for health.

An illustrative case

A couple in their mid thirties plan to conceive within a year. She has hypothyroidism, a BMI of 31 and heavy periods; he has a BMI of 33, smokes and uses testosterone bought online to support his gym training.

Her plan includes folic acid at the dose her doctor recommends given her weight, an iodine containing prenatal supplement, iron studies revealing deficiency that is treated, and a thyroid review with a plan for dose adjustment once pregnant. Both partners work on diet and activity together. He stops smoking and, crucially, stops testosterone under medical supervision, with an explanation that it suppresses sperm production and that recovery can take months. His semen analysis after 6 months shows recovery. They conceive in the following year, with her thyroid treatment adjusted promptly.

Preparing for 2, together

Preconception care works best as a shared project for both partners, beginning months before conception. Its elements are simple, largely inexpensive and backed by good evidence, and they give a pregnancy the best possible start.