What you eat before pregnancy helps build the nutrient stores your baby will rely on in the very first weeks, often before you know you are pregnant. The good news is that the most important steps are simple and inexpensive. This guide explains which supplements are recommended, what a balanced diet looks like, and why weight matters.
Folic acid: the most important supplement
Folic acid is a B vitamin that helps prevent neural tube defects, which are serious problems of the baby's brain and spine such as spina bifida. The neural tube forms very early in pregnancy, so the vitamin needs to be in your body before you conceive.
- Start earlyWHO and CDC advise starting at least 1 month before pregnancy. The NHS suggests ideally 3 months before.
- Take 400 micrograms a dayThis is the standard daily dose for anyone who could become pregnant, on top of folate from food.
- Continue to 12 weeksKeep taking it through the first 12 weeks of pregnancy, or longer if your doctor advises.
- Ask if you need moreA higher prescribed dose (5 mg in the UK) is advised for some people. See the list below.
- A previous pregnancy affected by a neural tube defect, or a personal or family history of one
- Diabetes
- Sickle cell disease or thalassaemia
- Taking medicine for epilepsy or HIV
If any of these apply, talk to your doctor before trying. A higher dose needs a prescription, and timing matters.
Vitamin D, iodine and iron
Folic acid is not the only nutrient that matters. A few others are worth checking before pregnancy, ideally with your doctor, because needs differ from person to person.
| Nutrient | Why it matters | Where to get it |
|---|---|---|
| Folic acid | Helps prevent neural tube defects | Daily 400 microgram supplement, plus leafy greens |
| Vitamin D | Supports healthy bones and teeth for your baby | Sunlight, oily fish, eggs; a 10 microgram supplement if advised |
| Iodine | Needed for thyroid hormones and baby's brain development | Iodised salt, seafood, dairy; some prenatal vitamins |
| Iron | Builds stores that help prevent anaemia in pregnancy | Lean meat, beans, leafy greens; supplements only if advised |
- Vitamin D: the NHS advises 10 micrograms a day in pregnancy during darker months, and all year if you get little sun on your skin. Do not take more than 100 micrograms a day.
- Iodine: the American Thyroid Association suggests a daily supplement with 150 micrograms of iodine for women in the US who are planning pregnancy. Needs vary by country, so ask your doctor.
- Iron: WHO says iron and folic acid supplements can be given to women planning pregnancy to improve iron stores. A simple blood test shows whether you need it.
Avoid vitamin A (retinol) supplements, cod liver oil and liver products in pregnancy. Too much vitamin A can harm a baby's development.
A balanced plate
There is no special fertility diet. A simple, balanced plate gives you most of what you need and supports a healthy weight.
- Half the plate: a variety of vegetables and fruit
- A quarter: whole grains such as brown rice, whole-wheat bread or oats
- A quarter: protein such as fish, eggs, beans, tofu, chicken or lean meat
- Water as your main drink
Fish and mercury
Fish provides protein and healthy fats, and is a good part of a pre-pregnancy diet. Some large fish contain more mercury, which can harm a developing baby, so the type of fish matters.
- Eat 8 to 12 ounces (about 2 to 3 palm-sized servings) of low-mercury fish a week, as the US FDA suggests
- Choose salmon, sardines, anchovies, cod, shrimp or canned light tuna
- Vary the types of fish you eat
- Shark, swordfish or marlin
- King mackerel, orange roughy, tilefish or bigeye tuna
- More than 2 portions of oily fish a week (NHS advice for pregnancy)
Everyday tips that make it easier
Good nutrition does not have to be complicated or expensive. Small, regular habits are easier to keep than big changes, and many fit naturally into Thai and Asian home cooking.
- Keep your folic acid next to your toothbrush so you remember it every day
- Add an extra vegetable dish or a portion of fruit to each meal
- Swap some white rice for brown rice or mixed grains
- Use iodised salt, but keep the total amount of salt moderate
- Choose water or unsweetened drinks instead of sugary drinks
- Bring your supplement bottles to your first doctor visit so they can be checked
More is not always better. Choose one prenatal vitamin that suits you rather than combining several products, and check the label for vitamin A (retinol).
Weight and BMI
Body weight affects hormones. According to ASRM, a BMI of 18.5 or less often causes irregular cycles and may stop ovulation. A BMI over 30 is linked to lower pregnancy rates and more pregnancy complications.
Weight also matters for men: ASRM notes that men with overweight or obesity more often have lower sperm counts and motility.
You do not need a perfect number. Talk with your doctor about a realistic, healthy goal, and focus on steady habits rather than strict diets.
Caffeine, vitamin A and supplement safety
| Drink | Approximate caffeine (NHS) |
|---|---|
| Cup of instant coffee | 100 mg (filter and shop coffee often more) |
| Cup of tea | 75 mg |
| Can of cola | 40 mg |
| 250 ml energy drink | 80 mg |
The NHS advises no more than 200 mg of caffeine a day in pregnancy, so it is sensible to get used to that limit while trying.
- Take 10 micrograms of vitamin D daily, year-round if you get little sun
- Ask your doctor about 5 mg folic acid if you have diabetes
- Take more than 100 micrograms of vitamin D a day
- Take cod liver oil or vitamin A (retinol) supplements, or eat liver
- Eat shark, swordfish or marlin
NHS limits for pregnancy: no more than 2 portions of oily fish a week, and no more than 4 cans or 2 steaks of tuna.
When to see a doctor
- You have diabetes, epilepsy, sickle cell disease or thalassaemia, or take regular medicine
- You or your partner have had a pregnancy affected by a neural tube defect
- You feel very tired or short of breath, which may be a sign of anaemia
- Your periods are irregular or have stopped
- You follow a restricted diet, such as vegan, or have an eating disorder
Questions & answers
Is folate from food enough?
Eating folate-rich foods is good, but WHO and CDC recommend a 400 microgram folic acid supplement in addition to food.
I am already pregnant and did not take folic acid. What should I do?
Start taking it as soon as you find out and continue until 12 weeks. Mention it to your doctor; there is no need to panic.
Should my partner take supplements too?
There is no standard supplement for men, but a balanced diet and healthy weight support sperm health.
Related DBN services
Related articles
Sources
- About Folic Acid — CDC
- Vitamins, supplements and nutrition in pregnancy — NHS
- Advice about Eating Fish — US FDA
- Weight and Fertility — ASRM ReproductiveFacts
- Hypothyroidism in Pregnancy — American Thyroid Association
- Foods to avoid in pregnancy — NHS