Nutrition in Pregnancy: Why It Matters More Than Most People Realise
What you eat during pregnancy directly influences fetal brain development, organ formation, birth weight, and long-term health outcomes for the child — as well as your own energy, immune function, and recovery after birth. Yet pregnancy nutrition is one of the most misunderstood areas in antenatal care. Most people receive either too little guidance (“eat well and take folic acid”) or too much conflicting information from unreliable sources. The aim here is to be specific and clear.
The Essential Nutrients in Pregnancy
Folic Acid / Folate
Folic acid (the synthetic form used in supplements) or folate (the natural form found in food) is the most important preconception and early pregnancy nutrient. It is essential for the formation of the neural tube — the structure that develops into the brain and spinal cord — which closes in the first 28 days of pregnancy, before most women even know they are pregnant. Neural tube defects (spina bifida, anencephaly) are significantly reduced by folic acid supplementation. The standard recommended dose is 400mcg daily, starting before conception and continuing through the first 12 weeks. Women who have previously had a pregnancy affected by a neural tube defect, who are on anti-epileptic medication, or who have a BMI above 30 require a higher dose — typically 5mg daily — and should discuss this with a doctor before conception.
Food sources of folate: dark leafy greens (spinach, kale, broccoli), lentils, chickpeas, fortified breakfast cereals, asparagus, and avocado. Dietary folate alone is typically insufficient to meet the requirement in early pregnancy — supplementation is essential.
Iron
Iron requirements increase substantially during pregnancy because blood volume expands by approximately 50% and the developing baby and placenta draw significant iron for their own development. Iron deficiency anaemia — the most common nutritional deficiency in pregnancy — causes fatigue, breathlessness, impaired immune function, and in severe cases, increased risk of preterm birth and low birth weight. Many pregnant women need an iron supplement in addition to dietary sources, particularly in the second and third trimesters.
Food sources: red meat and offal (liver is extremely high in iron but should be limited due to very high vitamin A content — see below), dark poultry meat, fortified cereals, lentils, beans, tofu, and dark leafy greens. Vitamin C consumed with plant-based iron significantly improves absorption. Tea, coffee, and calcium consumed at the same time inhibit iron absorption — space them by at least an hour from iron-rich meals.
Calcium
Calcium is essential for the development of the baby’s bones and teeth. If dietary calcium is insufficient, the baby will draw calcium from the mother’s bones, increasing her long-term osteoporosis risk. The requirement in pregnancy is approximately 1,000mg per day. Dairy products (milk, yoghurt, cheese) are the richest sources, but calcium is also found in fortified plant milks, canned fish with bones (sardines, salmon), almonds, sesame seeds (tahini), and fortified orange juice. Women who are dairy-free or vegan should discuss calcium supplementation with a healthcare provider.
Vitamin D
Vitamin D is essential for calcium absorption, fetal bone development, immune function, and is associated with reduced risk of gestational diabetes and pre-eclampsia. The majority of pregnant women worldwide are deficient or insufficient. Sun exposure is the primary source, but this is unreliable for much of the year in many climates. Supplementation with at least 400–1,000 IU (10–25mcg) daily is recommended throughout pregnancy and breastfeeding. Women with darker skin, limited sun exposure, or obesity are at higher risk of deficiency and may need higher doses.
Omega-3 Fatty Acids (DHA/EPA)
Docosahexaenoic acid (DHA) is critical for fetal brain and eye development, particularly in the third trimester when rapid brain growth occurs. The fetus relies entirely on maternal supply. Oily fish — salmon, sardines, mackerel, trout — are the richest dietary sources and are safe and beneficial in pregnancy at 2–3 portions per week. Women who do not eat fish should take an algae-based omega-3 supplement providing at least 200–300mg of DHA daily.
Iodine
Iodine is essential for thyroid hormone production, which drives fetal brain development. Iodine deficiency in pregnancy — even mild deficiency — is associated with lower IQ and cognitive impairment in the child. It is the most common preventable cause of intellectual disability worldwide. Sources include dairy products, eggs, seafood, and iodised salt. Pregnancy multivitamins should contain iodine (150mcg) — check the label, as not all do.
Foods to Eat More Of
The best pregnancy diet is diverse, minimally processed, and nutrient-dense. Prioritise: vegetables and fruit in a wide range of colours; whole grains (oats, brown rice, quinoa, wholegrain bread) for sustained energy and fibre; quality protein (eggs, legumes, lean meat, fish, dairy, tofu) at every meal; healthy fats (olive oil, avocado, nuts, seeds, oily fish); and adequate hydration — at least 8–10 glasses of water daily. Many women experience food aversions in the first trimester that make eating varied and nutritious food difficult. This is normal. Prioritise what can be tolerated, focus on calorie adequacy, take a prenatal multivitamin, and know that most women emerge from first-trimester nausea and expand their diet naturally.
Foods and Substances to Avoid Completely
Alcohol
No safe level of alcohol in pregnancy has been established. Alcohol crosses the placenta freely and can cause foetal alcohol spectrum disorders (FASD) — a range of permanent physical, behavioural, and cognitive impairments. The most severe form, foetal alcohol syndrome, causes distinctive facial features, growth restriction, and intellectual disability. Alcohol should be avoided completely throughout pregnancy. This is not a judgement — it is evidence-based guidance to protect the developing brain.
High-Mercury Fish
Large predatory fish accumulate mercury — a neurotoxin that damages the developing fetal brain and nervous system. Species to avoid completely during pregnancy: shark, swordfish, marlin, and tilefish. Species to limit: tuna (canned tuna is lower in mercury than fresh or tinned tuna steaks — limit canned tuna to 4 cans per week; limit fresh tuna to one portion per week). Oily fish that are low in mercury (salmon, sardines, mackerel, trout) remain safe and beneficial.
Raw or Undercooked Meat, Poultry, and Seafood
Raw and undercooked meats carry risk of toxoplasma (a parasite that can cause severe fetal infection), Listeria, Salmonella, and E. coli. All meat should be cooked until no pink remains and juices run clear. Raw shellfish (oysters, clams) and sushi made with raw fish should be avoided. Smoked fish (smoked salmon) is generally safe when purchased fresh and consumed promptly, but home-cured or unpackaged smoked fish poses Listeria risk.
Unpasteurised Dairy and Soft Cheeses
Listeria monocytogenes — a bacterium that can cross the placenta and cause miscarriage, stillbirth, or severe neonatal infection — is the primary concern. Foods to avoid: unpasteurised (raw) milk and cheeses; mould-ripened soft cheeses including Brie, Camembert, and blue cheeses made from any milk (even pasteurised, these can harbour Listeria due to their moist environment); and unpasteurised pâté. Hard cheeses (cheddar, parmesan, Edam), processed cheeses, cream cheese, cottage cheese, and mozzarella are all safe.
Raw Eggs and Foods Containing Them
Raw eggs carry Salmonella risk. Avoid raw egg dishes: homemade mayonnaise, hollandaise sauce, uncooked cake batter, mousse, and some ice creams made with raw egg. Commercial versions of these products (pasteurised egg) are safe. In many countries, eggs that are certified and stamped from vaccinated hens (the British Lion Mark system, for example) have been shown to be extremely low risk and can be eaten runny.
Liver and Liver Products
Liver is extraordinarily high in vitamin A (retinol). Excessive preformed vitamin A (from animal sources) in pregnancy is teratogenic — it can cause birth defects, particularly affecting the head, face, heart, and brain. Liver, liver pâté, and liver sausage should be avoided. Vitamin A from plant sources (beta-carotene, found in carrots, sweet potatoes, and orange vegetables) does not carry this risk.
Caffeine
High caffeine intake during pregnancy is associated with increased risk of miscarriage and restricted fetal growth. The recommended limit is no more than 200mg of caffeine per day. A standard mug of instant coffee contains approximately 100mg; brewed coffee 140mg; a can of cola 40mg; a mug of tea 75mg. Staying within the 200mg limit while enjoying moderate coffee or tea is manageable for most people.
Managing Common Nutrition Challenges
Morning sickness in the first trimester makes eating well difficult for many women. Small, frequent meals and foods that are cold or room temperature (which produce less odour) often help. Ginger in various forms (ginger tea, ginger biscuits) has reasonable evidence for reducing nausea. Vitamin B6 (pyridoxine) supplements at 25mg three times daily are safe and effective for pregnancy nausea. Heartburn worsens as pregnancy progresses due to the growing uterus pushing the stomach upward — smaller meals, avoiding lying down after eating, and pregnancy-safe antacids manage this for most women. Constipation from progesterone-driven slower gut motility is common and addressed by increasing dietary fibre, fluid intake, and safe physical activity.