Pregnancy Nutrition: Essential Vitamins and What to Avoid

You need more of certain vitamins during pregnancy — specifically folic acid, vitamin D, iron, and calcium — and you need to avoid some foods and supplements entirely. A healthy pregnancy diet isn't complicated, but it is specific. This guide walks through what you need, when you need it, and what to skip to keep both you and your growing baby safe.

Why Pregnancy Nutrition Matters

Your body supports two people now: you and your developing baby. Between conception and birth, your baby's organs, bones, brain, and immune system all develop from the nutrients you consume. Getting the right vitamins and minerals doesn't require eating twice as much — it requires eating smarter.

The NHS recommends several key supplements starting before pregnancy and continuing through birth and breastfeeding. Why? Because whole-food sources alone don't always provide enough of what you need, particularly for folic acid and vitamin D in the UK climate.

Some foods that are perfectly safe normally become risky during pregnancy because they can carry infections that pose a particular threat to a developing baby. Other supplements and substances — even some vitamins in high doses — need to be avoided.

The Essential Vitamins and Minerals Your Baby Needs

Folic Acid (Vitamin B9)

The number: 400 micrograms (mcg) daily, starting before conception and continuing through the first 12 weeks of pregnancy.

Why it matters: Folic acid reduces the risk of neural tube defects (like spina bifida) by around 70%. Your baby's neural tube forms very early — often before you know you're pregnant — so folic acid from before conception makes a real difference.

Where to get it: The NHS recommends a 400mcg folic acid supplement. Many foods contain folate (the natural form), including leafy greens, lentils, chickpeas, and fortified cereals, but supplementation is the safest way to guarantee you hit that 400mcg target.

Vitamin D

The number: 10 micrograms (400 IU) daily throughout pregnancy and while breastfeeding.

Why it matters: Vitamin D helps your baby's bones develop and supports immune function. In the UK, particularly during winter months, most people don't produce enough vitamin D from sunlight alone. Deficiency in pregnancy is linked to gestational diabetes, preeclampsia, and lower birth weight.

Where to get it: The NHS recommends supplements for all pregnant people, regardless of skin tone. You can get some from fatty fish (salmon, mackerel), egg yolks, and fortified milk, but supplementation is the reliable route. If you're vegan, check your supplement is vegan-certified (usually derived from lichen, not animal products).

Iron

The number: Your iron needs increase to 27mg daily (compared to 18mg for non-pregnant women). Most prenatal vitamins include this.

Why it matters: Your blood volume increases by about 50% during pregnancy. Iron makes the hemoglobin that carries oxygen to your baby. Without enough iron, you become anemic, which increases fatigue, breathlessness, and risks during labor.

Where to get it: Red meat, poultry, beans, lentils, and fortified cereals all contain iron. Pair them with vitamin C (orange juice, strawberries, peppers) to boost absorption. If blood tests show you're deficient, your midwife will recommend an iron supplement.

Calcium

The number: 700mg daily (the same as non-pregnant women, but your body absorbs it more efficiently during pregnancy).

Why it matters: Your baby's skeleton is building at full speed. If you don't consume enough calcium, your body will leach it from your bones to give to your baby — that's non-negotiable. Calcium also helps regulate blood pressure and reduces preeclampsia risk.

Where to get it: Dairy (milk, yogurt, cheese), fortified plant-based milks, leafy greens, and almonds. Three glasses of milk or equivalent cover your daily need. If you're lactose intolerant, lactose-free milk or fortified alternatives work just as well.

Vitamin B12

The number: 2.4 micrograms daily.

Why it matters: B12 supports neurological development and red blood cell formation. Deficiency is rare in people eating animal products but common in vegans and vegetarians — and it can affect your baby's brain development.

Where to get it: Meat, fish, eggs, dairy, and fortified cereals. If you're vegan, you must supplement B12; it's not a "consider it" — it's essential.

Docosahexaenoic Acid (DHA)

The number: 200–300mg daily (omega-3 fatty acid).

Why it matters: DHA is crucial for your baby's brain and eye development. Studies show adequate DHA is associated with better visual and cognitive development in infants.

Where to get it: Fatty fish (2–3 portions per week is the NHS recommendation, with certain fish limited due to mercury). If you don't eat fish, algae supplements are the vegan alternative. Some prenatal vitamins include DHA — check yours.

Nutrition by Trimester

First Trimester (Weeks 1–12)

You don't need more calories in the first trimester — the "eating for two" myth is just that, a myth — but nutrient density matters more than quantity. Focus on:

Folic acid supplement (critical window)
Vitamin D
Small, frequent meals if morning sickness makes large meals unappealing
Ginger or B6 supplements for nausea (both have NHS approval for pregnancy use)

Nausea and food aversions are common. If you can't stomach vegetables, prioritize other nutrient sources (eggs, yogurt, fortified grains) and know it's temporary.

Second Trimester (Weeks 13–27)

Your appetite likely returns, and your baby's growth accelerates. Add roughly 300 extra calories per day — that's a snack, not a second meal. Focus on:

Iron (increased from 18mg to 27mg daily)
Calcium for bone development
Protein (71g daily, up from 46g) for tissue growth
Regular meals to maintain stable blood sugar

This is when you should gain most of your weight. Check our guide to pregnancy BMI to understand your target weight gain range.

Third Trimester (Weeks 28–40)

Your baby is packing on weight fast. Add another 200 calories per day. Focus on:

Continued iron and calcium
Protein (still 71g daily)
Fiber (to manage constipation, which is common)
Adequate fluids (dehydration increases Braxton-Hicks contractions)

Heartburn and reflux intensify as your baby compresses your stomach. Small, frequent meals help more than large ones.

Foods and Supplements to Avoid During Pregnancy

Foods to Avoid Entirely

Raw or undercooked meat, poultry, eggs, and seafood — Risk: Listeria, E. coli, Salmonella, which can cause miscarriage, stillbirth, or severe illness in newborns.

Unpasteurized dairy, soft cheeses, and pâté — Risk: Listeria. This includes brie, camembert, blue cheese, feta, and some mozzarellas. Hard cheeses like cheddar are safe (the acid makes them hostile to Listeria).

High-mercury fish — Shark, swordfish, king mackerel, marlin. Limit tuna to two cans per week (or one fresh steak). Safe fish: salmon, mackerel, sardines, trout, and white fish.

Alcohol — No safe level is established. Even small amounts cross the placenta and can harm your baby's development.

Raw sprouts — Alfalfa, mung bean, radish. Risk: E. coli and Salmonella.

Unwashed vegetables — Toxoplasma risk (from soil or cat feces). Always wash, even if you're buying pre-washed salad.

Herbal teas — Some are safe (ginger, lemon balm), others aren't (sage, parsley in medicinal amounts, licorice). Stick to commercial brands labeled safe for pregnancy.

Supplements to Avoid or Limit

Vitamin A (retinol) in high doses — Excess vitamin A is teratogenic. The RDA is 770mcg; above 3,000mcg daily increases birth defect risk. Avoid cod liver oil supplements (very high in retinol) and look for beta-carotene supplements instead (the body converts it to vitamin A as needed, so the risk is lower).

Vitamin E supplements — Avoid high-dose supplements (above the RDA of 15mg). Food sources are fine.

Herbal supplements — Ephedra, ma huang, ginseng, and black cohosh have not been tested in pregnancy and should be avoided. Always check with your midwife before starting any supplement.

Caffeine above 200mg per day — This is not a mineral or vitamin, but worth noting: more than 200mg daily (roughly two cups of regular coffee) is linked to miscarriage risk. Switch to decaf or limit to one cup.

Mental Health and Body Changes During Pregnancy

Your body is changing rapidly, and hormonal shifts affect mood and anxiety. Read about recognizing signs of perinatal depression. Good nutrition supports mental health too — stable blood sugar from regular meals and adequate protein reduces mood crashes.

Frequently Asked Questions

Q: Do I need a prenatal vitamin, or is food enough? A: Food is a great foundation, but prenatal vitamins are strongly recommended by the NHS. Folic acid and vitamin D are the big two — it's very difficult to hit folic acid targets (400mcg) from food alone, and UK sunlight isn't reliable for vitamin D. A standard prenatal vitamin covers these plus iron and B vitamins. Check the label to see what's included.

Q: I'm vegan. Can I get all the nutrients I need from food? A: Almost, but not quite. You'll need B12 and vitamin D supplements (the same as non-vegan pregnant people). DHA ideally comes from algae supplements. Iron, calcium, and folate can come from plant sources if you eat strategically — beans, lentils, fortified cereals, and leafy greens. Work with a dietitian to make sure you're hitting targets.

Q: What if I have food aversions and can't eat vegetables? A: Morning sickness and aversions are temporary. Prioritize nutrient-dense foods you can tolerate — eggs, yogurt, fortified grains, nuts, and seeds. Your prenatal vitamin covers gaps. Ginger and B6 (25mg three times daily) have NHS evidence for nausea relief.

Q: Can I exercise while pregnant? A: Yes. The NHS recommends 150 minutes of moderate activity per week unless your midwife advises otherwise. Walking, swimming, and prenatal yoga are popular. Avoid contact sports and activities with a high fall risk. Exercise improves mood, reduces gestational diabetes risk, and tends to lead to shorter labors.

Q: I'm over 35. Does that change my nutrition needs? A: Not significantly. Your calorie and micronutrient targets are the same. Pregnancy after 35 carries different medical risks, but nutrition is not one of them. Prenatal care and screening matter more.

Q: How much weight should I gain? A: It depends on your pre-pregnancy BMI. A healthy-weight woman (BMI 18.5–24.9) should gain 11.5–16kg. Underweight women (BMI <18.5) should gain more; overweight or obese women should gain less. Check our pregnancy BMI guide, then track progress with your midwife.

Q: Can I diet during pregnancy? A: No. Pregnancy is not the time to lose weight. If you're overweight, your midwife will encourage adequate nutrition to support your baby. After birth and breastfeeding, weight loss is possible.

Q: What about prenatal testing and nutrition timing? A: Nutrition matters at every stage, but certain vitamins are critical at specific windows. Folic acid in the first 12 weeks (neural tube closure), vitamin D and calcium throughout (bone development), and iron especially in the second and third trimesters (blood volume expansion and baby's iron stores). Track your milestones week by week to stay aligned with your baby's needs at each stage.

Next Steps

Start a prenatal vitamin containing folic acid and vitamin D as soon as you're planning pregnancy (or immediately if you've just found out you're pregnant). Share this guide with your midwife if you have specific questions about your diet.

Track your pregnancy milestones week by week to stay aligned with your baby's nutritional needs. If you're thinking about the financial side of pregnancy and parenting, check our baby budget planner to understand the costs ahead.