Pregnancy Nutrition: What to Eat, What to Avoid, and Key Supplements

Two supplements are universally recommended for all pregnant women in the UK, regardless of dietary quality: folic acid and vitamin D.

Folic acid (the synthetic form of folate, vitamin B9) is the most critical supplement in early pregnancy. It is essential for neural tube development — the formation of the brain and spinal cord — which occurs in the first 28 days after conception, often before a woman knows she is pregnant. Adequate folic acid reduces the risk of neural tube defects (such as spina bifida) by up to 70 per cent. The NHS recommends 400 micrograms daily from the time you begin trying to conceive until 12 weeks of pregnancy. Women with a personal or family history of neural tube defects, those taking anti-epileptic medication, or those with a BMI over 30 are advised to take a higher dose (5mg daily) — speak with your GP.

Folate from food sources (dark leafy greens, lentils, chickpeas, fortified cereals, avocado, asparagus, broccoli) is valuable throughout pregnancy, particularly in the second and third trimesters when requirements remain elevated at 300–600 micrograms daily. However, folate from food alone is insufficient in early pregnancy given the critical timing and variable absorption, which is why a supplement is essential.

Vitamin D is recommended at 10 micrograms (400 IU) daily throughout pregnancy and breastfeeding by the NHS. Vitamin D supports foetal bone development, immune function, and may reduce the risk of gestational diabetes and pre-eclampsia. Women with darker skin tones, limited sun exposure, obesity, or who cover most of their skin are at higher risk of deficiency and may need higher doses under medical supervision. Dietary sources of vitamin D are limited (egg yolks, fortified foods, oily fish) so supplementation is practical and widely available.

Beyond folic acid and vitamin D, several nutrients play critical roles in pregnancy and warrant particular dietary attention.

Iron requirements increase substantially in pregnancy to support the expanding blood volume (which increases by 40–50 per cent) and the building of foetal iron stores. The NHS recommends eating iron-rich foods regularly — red meat, poultry, fish, lentils, beans, fortified cereals, dark leafy greens — alongside vitamin C to enhance absorption. Routine iron supplementation is not recommended for all pregnant women in the UK (unlike some other countries) unless blood tests show deficiency, as high iron can cause constipation and other issues.

Calcium is required for the baby's bone and tooth development. If maternal calcium intake is insufficient, the foetus draws calcium from the mother's bones. Aim for 700–1,000mg daily from dairy or dairy alternatives, tinned fish with bones, tofu, and green vegetables. Women under 25, whose own bones are still mineralising, have particularly high calcium needs during pregnancy.

Iodine is essential for foetal thyroid hormone production and brain development. Iodine deficiency during pregnancy is a leading preventable cause of intellectual disability globally. Dairy foods, seafood, and iodised salt are the main dietary sources in the UK. Many pregnancy multivitamins do not contain iodine, so check your supplement label — if it does not contain iodine, consider adding a separate supplement of 150 micrograms daily, or discuss with your midwife.

Omega-3 DHA supports foetal brain and retinal development. Oily fish (salmon, sardines, mackerel, herring) provides the most bioavailable DHA. The recommendation is two to three portions of oily fish per week during pregnancy, staying within a maximum of two portions of high-mercury species (see below). Plant-based DHA from algae supplements is an effective alternative for those who do not eat fish.

Choline, found in eggs, meat, fish, and legumes, supports neural tube closure and brain development and is often overlooked in prenatal nutrition. Two eggs per day covers a significant proportion of pregnancy choline needs.

The foundation of good pregnancy nutrition is not dramatically different from good nutrition in general — it is a varied, whole-food diet with greater attention to specific nutrients. There are no foods you need to eat that you would not normally recommend, and the concept of 'eating for two' is a calorie myth: additional energy requirements in pregnancy are modest (approximately 200–300 extra calories per day in the third trimester only).

Protein needs increase during pregnancy to approximately 70–100 grams per day to support foetal tissue growth, placental development, and the expansion of maternal blood volume. Include a quality protein source at each meal: eggs, meat, fish, dairy, legumes, tofu, tempeh, or Greek yoghurt. Women experiencing nausea who struggle to eat much should prioritise protein-rich foods when they can, as protein is the nutrient most likely to suffer from food aversion and restriction.

Complex carbohydrates provide the glucose that is the foetus's primary fuel. Wholegrains (oats, brown rice, wholemeal bread, quinoa), legumes, sweet potatoes, and fruit provide sustained energy alongside fibre, which helps prevent the constipation that commonly troubles pregnant women. Aim for 25–35 grams of fibre daily, increasing fluid intake alongside any fibre increase.

Healthy fats — particularly omega-3s from oily fish, walnuts, and flaxseed; and monounsaturated fats from olive oil and avocado — support the absorption of fat-soluble vitamins and foetal brain development. Colourful vegetables and fruit provide folate, vitamin C, potassium, antioxidants, and fibre; aim for at least five portions daily, prioritising dark leafy greens, orange and yellow vegetables, and berries.

Staying well hydrated is also important — blood volume increases significantly, and mild dehydration can trigger headaches and Braxton Hicks contractions. Aim for around two litres of fluid daily, primarily water.

Some foods carry genuine safety risks in pregnancy due to bacterial contamination, harmful toxins, or substances that cross the placenta. Understanding these clearly — rather than following overcautious advice — allows informed decision-making.

Listeria monocytogenes is a bacterium that can cause listeriosis, a rare but potentially serious infection in pregnancy. Foods to avoid due to listeria risk include unpasteurised soft cheeses (brie, camembert, soft blue cheeses), pâté of any type (including fish and vegetable pâté), unpasteurised milk, and ready-to-eat cold-smoked fish. Hard cheeses (cheddar, parmesan), pasteurised soft cheeses (cream cheese, ricotta, cottage cheese), and cooked soft cheeses are all safe.

Salmonella risk is associated with raw or undercooked eggs and poultry. In the UK, lion-stamped eggs are considered safe to eat runny or raw during pregnancy. Ensure all poultry is fully cooked through, and avoid products containing raw unpasteurised eggs (such as homemade mayonnaise from non-lion-stamped eggs).

Toxoplasma gondii is a parasite found in raw and undercooked meat, unwashed soil, and cat faeces. Cook all meat thoroughly, wash all fruit and vegetables carefully, and wear gloves when gardening or handling cat litter. Cured/cold meats like salami and Parma ham carry some toxoplasma risk and are best avoided or frozen for four days before eating.

High-mercury fish should be limited. Shark, swordfish, and marlin should be avoided entirely; tuna should be limited to two steaks or four medium tins per week. Mercury accumulates in the foetal nervous system and can impair brain development. Other oily fish (salmon, sardines, mackerel, trout) are safe within the two-to-three portions per week recommendation.

Alcohol should be avoided entirely during pregnancy. There is no established safe level, and foetal alcohol spectrum disorder (FASD) is a leading preventable cause of developmental disability. Caffeine should be limited to under 200mg per day (roughly two mugs of coffee or one shot espresso) — higher intakes are associated with increased miscarriage risk and lower birth weight.

Up to 80 per cent of pregnant women experience nausea and vomiting in the first trimester, and for around one per cent it progresses to hyperemesis gravidarum — severe, persistent vomiting requiring medical treatment. Nausea peaks typically between six and twelve weeks and is thought to be triggered by the rapid rise in hCG (human chorionic gonadotropin) and oestrogen in early pregnancy.

Nutritionally, several strategies can reduce nausea severity and manage its impact on intake. Eating small, frequent meals every two to three hours prevents the stomach from becoming empty, which worsens nausea. Bland, dry, starchy foods — crackers, dry toast, plain rice, plain biscuits — are often the most tolerable and help settle the stomach. Cold foods and drinks generally have less smell than hot foods, which can be helpful as heightened smell sensitivity often triggers nausea.

Ginger has the strongest evidence of any dietary supplement for pregnancy nausea. Studies support doses of 250mg of ginger four times daily, equivalent to fresh ginger root in tea, ginger biscuits, or ginger capsules. Ginger ale (made with real ginger) and crystallised ginger are also useful. Vitamin B6 (pyridoxine) has shown benefit in multiple trials at doses of 10–25mg three times daily and is often recommended alongside ginger or as a first-line treatment by obstetricians.

Separating solid food and fluids — drinking between meals rather than with them — can reduce nausea by preventing gastric distension. Cold water, sparkling water, ice chips, herbal teas (ginger, peppermint, chamomile), and diluted fruit juice are generally better tolerated than large volumes with meals.

If nausea is severe and preventing adequate nutrition for more than two weeks, or if you are losing weight or becoming dehydrated, seek medical help promptly. Hyperemesis gravidarum requires medical management and often intravenous fluids.

While the first trimester is dominated by food avoidance and managing nausea, the second and third trimesters are when the foetus grows most rapidly and nutritional demands truly escalate. Most women find appetite returns and food tolerance broadens significantly after week 12.

The second trimester is often called the 'golden period' of pregnancy — energy levels improve, nausea recedes, and appetite normalises. This is the time to focus on building nutritional reserves. Iron requirements increase as blood volume expands; calcium, phosphorus, and magnesium are needed for the rapid mineralisation of foetal bones; and DHA is particularly important for the brain growth spurt that begins around week 20.

By the third trimester, the foetus gains approximately 50 per cent of its birth weight and nutritional demands are at their highest. The stomach is compressed by the growing uterus, making large meals uncomfortable — smaller, more frequent meals work better. Heartburn is very common and is worsened by spicy foods, fatty foods, caffeine, and eating close to lying down. Sleeping with the upper body slightly elevated and eating the evening meal at least two to three hours before bed helps.

Constipation is another common third trimester complaint, addressed by adequate fibre, hydration, and gentle physical activity. Prunes and prune juice have a gentle laxative effect and also provide iron — a useful dual action in late pregnancy.

Caloric needs in the third trimester increase by around 200 calories per day compared to pre-pregnancy — equivalent to a small extra snack such as a banana with almond butter, a glass of milk with a handful of nuts, or a pot of Greek yoghurt with berries. This is the only trimester where caloric intake needs deliberate adjustment; the first and second trimesters do not require additional calories.