Omega-3 and DHA in Pregnancy: Do You Need Supplements?

Medically reviewed content. Last updated: April 2026.

DHA (docosahexaenoic acid) is an omega-3 fatty acid that plays a critical role in your baby's brain and eye development, particularly during the third trimester when brain growth accelerates. This guide explains how much you need, the best sources, and whether a supplement is worthwhile.

Why is DHA important during pregnancy?

Your baby's brain undergoes rapid development throughout pregnancy, but especially in the last trimester. DHA is a structural component of brain tissue and the retina. It accumulates in your baby's brain at a particularly high rate during the final weeks of pregnancy and the first two years of life.

Research suggests that adequate DHA intake during pregnancy may support healthy brain and visual development, contribute to a slightly longer gestational period (reducing the risk of early preterm birth), and support your own mood and mental health during pregnancy and postpartum.

A 2018 Cochrane review of omega-3 supplementation in pregnancy found a modest reduction in the risk of preterm birth (before 37 weeks) and early preterm birth (before 34 weeks).

How much do you need?

There is no official UK government recommendation for DHA intake during pregnancy. However, expert bodies provide the following guidance:

• The European Food Safety Authority (EFSA) recommends an additional 100 to 200mg of DHA per day during pregnancy, on top of the general adult recommendation of 250mg combined EPA and DHA
• The International Society for the Study of Fatty Acids and Lipids (ISSFAL) recommends at least 200mg DHA per day during pregnancy
• The FAO/WHO recommend 200 to 300mg DHA daily for pregnant and breastfeeding people

In practical terms, aiming for at least 200 to 300mg of DHA per day is a reasonable target.

What are the best food sources?

Oily fish

Oily fish is the richest dietary source of DHA and EPA. The NHS recommends eating up to two portions of fish per week during pregnancy, with at least one portion being oily fish. Good options include:

• Salmon (a 140g portion provides roughly 1,000 to 2,000mg of omega-3)
• Mackerel (not king mackerel, which is high in mercury)
• Sardines
• Herring
• Anchovies
• Trout

Fish to limit or avoid

Some fish contain higher levels of mercury, which can harm your baby's developing nervous system. During pregnancy, avoid shark, swordfish, and marlin entirely. Limit tuna to no more than two fresh tuna steaks or four medium tins per week.

Other food sources

• Eggs (particularly those enriched with omega-3)
• Some fortified foods (certain milks, yoghurts, and breads)

Plant sources such as flaxseeds, chia seeds, walnuts, and hemp seeds contain ALA (alpha-linolenic acid), a different type of omega-3. Your body can convert ALA to DHA, but the conversion rate is very low (around 5 to 10%), making these sources insufficient as a sole supply of DHA.

Do you need a supplement?

If you eat two portions of fish per week (including one oily fish), you are likely getting enough DHA from your diet. A supplement may not be necessary.

Consider a DHA supplement if:

• You do not eat fish or eat it rarely
• You follow a vegetarian or vegan diet
• You dislike the taste or smell of fish
• You have been advised to limit fish intake for any reason

What type of supplement?

Fish oil supplements. Choose one that provides at least 200 to 300mg DHA per day. Look for supplements specifically marketed for pregnancy, as these have been tested for mercury and other contaminants. Avoid cod liver oil, as it contains high levels of vitamin A (retinol), which can be harmful during pregnancy.

Algae-based DHA supplements. These provide DHA derived directly from microalgae (the original source that fish get their DHA from). They are suitable for vegetarians and vegans and are free from mercury and other fish-related contaminants. Look for at least 200 to 300mg DHA per capsule.

What about EPA?

EPA (eicosapentaenoic acid) is another omega-3 fatty acid found in fish oil. While DHA is the priority during pregnancy for brain development, EPA also has anti-inflammatory properties and may support cardiovascular health and mood. Most fish oil and algae supplements contain both DHA and EPA.

Is it safe to take omega-3 supplements during pregnancy?

Yes, omega-3 supplements (fish oil or algae-based) are considered safe during pregnancy at recommended doses. The main precautions are:

• Do not take cod liver oil (contains too much vitamin A)
• Choose supplements tested for heavy metals and contaminants
• Stick to recommended doses (there is no benefit to mega-dosing)
• If you are taking blood-thinning medication, consult your GP before starting omega-3 supplements, as high doses can have a mild blood-thinning effect

Key takeaways

• DHA is essential for your baby's brain and eye development, particularly in the third trimester
• Aim for at least 200 to 300mg DHA per day from food or supplements
• Oily fish is the best dietary source: eat up to two portions per week, including salmon, sardines, mackerel, or trout
• Avoid high-mercury fish (shark, swordfish, marlin) and limit tuna
• If you do not eat fish, an algae-based DHA supplement is the best alternative
• Avoid cod liver oil during pregnancy due to high vitamin A content
• Plant-based omega-3 (ALA from flaxseeds and walnuts) does not convert efficiently to DHA

Sources

• NHS. Fish and shellfish in pregnancy. nhs.uk
• EFSA. Scientific opinion on dietary reference values for fats. 2010
• Middleton P et al. Omega-3 fatty acid addition during pregnancy. Cochrane Database of Systematic Reviews. 2018
• SACN. Advice on fish consumption: benefits and risks. 2004
• RCOG. Healthy eating in pregnancy. Patient information. 2023
• FAO/WHO. Fats and fatty acids in human nutrition: report of an expert consultation. 2010