Omega-3 in Pregnancy: How to Get Enough — A Dietitian's Guide

6 days ago

8 min read

Sophie Mumby, Registered Dietitian (HCPC)

Omega-3 is something I get asked about a lot in my clinics, particularly during pregnancy.

How much do you actually need? Which fish are safe to eat? Do you need an omega-3 supplement? And what if you don't eat fish?

There is a huge amount of conflicting information online, so in this guide I'll explain what omega-3 is, why it matters during pregnancy, how to get enough from your diet and when a supplement might be worth considering.

What are omega-3 fatty acids?

Omega-3 fatty acids are a type of polyunsaturated fatty acid. There are three main types:

EPA (eicosapentaenoic acid)
DHA (docosahexaenoic acid)
ALA (alpha-linolenic acid)

ALA contains 18 carbon atoms, while EPA and DHA are longer-chain fatty acids containing 20 and 22 carbon atoms respectively.

ALA is an essential fatty acid, meaning our bodies cannot make it and we therefore need to obtain it from our diet.

We can convert small amounts of ALA into EPA and DHA in the body, but this conversion is limited. This is one reason why dietary sources of EPA and DHA are particularly important during pregnancy.

Why is omega-3 important during pregnancy?

DHA is particularly important during pregnancy because it contributes to the normal development of the baby's brain and eyes.

The developing baby receives DHA from the mother, which means that maternal dietary intake is an important source.

EPA and DHA also have wider roles in the body, including supporting cell membranes and normal cardiovascular and immune function.

There is also considerable interest in omega-3 during pregnancy because of its potential relationship with preterm birth.

A large Cochrane review of 70 randomised controlled trials involving almost 20,000 pregnant women found that increasing long-chain omega-3 intake during pregnancy was associated with an 11% lower risk of preterm birth before 37 weeks and a 42% lower risk of early preterm birth before 34 weeks.

However, this doesn't mean that every pregnant woman needs to take a high-dose supplement. The evidence around supplementation is more nuanced, and current UK guidance does not recommend a specific high-dose omega-3 supplement for everyone.

Where do omega-3s come from?

Oily fish: the richest dietary source of EPA and DHA

EPA and DHA are found in particularly high amounts in oily fish.

Examples include:

Salmon
Sardines
Mackerel
Herring
Pilchards

Some shellfish, including crab and oysters, also provide EPA and DHA, although generally in smaller amounts than oily fish.

Plant foods such as flaxseed, chia seeds and walnuts provide ALA. These are still valuable foods to include during pregnancy, but because conversion of ALA to EPA and DHA is limited, they cannot be considered equivalent to oily fish as a source of long-chain omega-3.

How much omega-3 do you need during pregnancy?

This is where things can become confusing because there isn't currently a specific UK government recommendation stating that every pregnant woman should take a particular number of milligrams of EPA and DHA each day.

Instead, UK healthy eating guidance recommends eating at least two portions of fish per week, including one portion of oily fish.

One portion is around 140g.

This is a practical way of obtaining EPA and DHA during pregnancy, while also providing other important nutrients such as protein, iodine, vitamin D and selenium.

What does 140g of fish actually provide?

The McCance and Widdowson's Composition of Foods Integrated Dataset (CoFID) gives us an idea of how much EPA and DHA different fish contain.

Approximate EPA + DHA content per 140g portion of uncooked fish:

Fish	EPA + DHA
Mackerel	3,570mg
Farmed salmon	3,038mg
Wild salmon	2,338mg
Herring	1,680mg
Sardines	1,554mg
Alaskan pollock	182mg
Cod	98mg

This highlights an important point: not all fish provide the same amount of omega-3.

Oily fish such as salmon, sardines, herring and mackerel are particularly rich sources of EPA and DHA, whereas white fish such as cod and pollock contain much smaller amounts.

The exact amount will vary depending on the species, where the fish comes from, what it has been fed and how it has been prepared, so these figures should be viewed as estimates rather than precise amounts.

What does EFSA say about omega-3 in pregnancy?

The European Food Safety Authority (EFSA) has established an Adequate Intake of 250mg of EPA + DHA per day for adults.

For pregnancy, EFSA recommends this same 250mg/day of EPA + DHA, plus an additional 100–200mg/day of preformed DHA.

It's important to put this into context: this is European guidance rather than a specific UK government pregnancy recommendation.

You also don't need to sit there calculating your omega-3 intake every day.

For most pregnant women, regularly including oily fish as part of a varied diet is a practical way of obtaining EPA and DHA.

Eating fish safely during pregnancy

Fish can absolutely be part of a healthy pregnancy diet, but there are some important safety considerations.

Avoid these fish during pregnancy

Shark, swordfish and marlin should be avoided because they can contain high levels of mercury.

Limit oily fish

You should have no more than two portions of oily fish per week during pregnancy.

This includes salmon, sardines, mackerel, herring and pilchards.

Limit tuna

You should have no more than:

4 medium-sized cans of tuna per week, or
2 tuna steaks per week

Tuna doesn't count towards your oily fish allowance.

What about white fish?

There is no specific weekly limit for white fish during pregnancy.

White fish such as cod, haddock and pollock can therefore be included regularly as part of a varied diet.

It's worth remembering, however, that white fish generally contains much less EPA and DHA than oily fish.

What about fish liver oil?

Avoid fish liver oil supplements, such as cod liver oil, during pregnancy.

This is because they can contain high levels of vitamin A (retinol), which can be harmful to the developing baby.

If you're considering an omega-3 supplement during pregnancy, choose a product that does not contain vitamin A/retinol.

What if you don't eat fish?

You can still have a healthy pregnancy without eating fish.

There are lots of reasons someone might not eat fish, including vegetarianism, veganism, allergies, food preferences, cost or simply not liking fish.

Eggs

Eggs contain small amounts of DHA.

For example, some food-composition databases report around 60mg DHA per 100g of chicken egg. Two medium eggs would therefore provide roughly 60–70mg DHA, although the amount varies.

Some eggs are also enriched with omega-3 because the hens are fed omega-3-rich feed such as flaxseed. These can provide considerably more DHA.

However, eggs are not equivalent to oily fish as a source of omega-3, and they contain very little EPA.

Don't overlook frozen and tinned fish

If cost is one of the reasons you don't eat much fish, it doesn't need to be fresh.

Frozen and tinned fish can be affordable, convenient and nutritious options.

Tinned salmon and sardines can be particularly useful ways of including oily fish without the cost of buying fresh fish every week.

Just remember to check the type of fish and the pregnancy safety guidance above.

What if I don't eat fish at all?

If you don't eat fish, an algae-derived omega-3 supplement can provide DHA and is a suitable option for people following a vegetarian or vegan diet.

Fish oil supplements can also provide EPA and DHA if you eat fish but don't regularly choose to eat oily fish.

Whether you would benefit from a supplement depends on your overall diet and individual circumstances.

If you're pregnant and considering an omega-3 supplement, check the label carefully and choose one that is suitable for pregnancy and does not contain vitamin A (retinol).

If you have previously had a preterm birth or are considered to be at increased risk of preterm birth, speak to your midwife or obstetric team about whether omega-3 supplementation is appropriate for you.

Does omega-3 reduce the risk of premature birth?

This is one of the most interesting areas of the evidence around omega-3 and pregnancy.

The 2018 Cochrane review found that increasing long-chain omega-3 intake during pregnancy was associated with:

an 11% reduction in preterm birth before 37 weeks
a 42% reduction in early preterm birth before 34 weeks
fewer babies with low birthweight

However, supplementation was also associated with a small increase in pregnancies continuing beyond 42 weeks.

The review authors suggested that pregnant women could consider 500–1000mg of long-chain omega-3 per day from around 12 weeks of pregnancy, with at least 500mg as DHA.

Importantly, this was the review authors' interpretation of the evidence, rather than a current UK government recommendation for all pregnant women.

If you are pregnant and have concerns about your individual risk of preterm birth, speak to your midwife or obstetric team rather than starting a high-dose supplement yourself.

What about grass-fed beef?

You may have seen claims on social media that grass-fed beef is a good source of omega-3.

Grass contains ALA, which contributes to the omega-3 content of the animal's diet. As a result, grass-fed beef does contain some omega-3 fatty acids and generally contains more than grain-fed beef.

However, the amounts are very small compared with oily fish.

A 2022 review estimated that grass-fed beef provided around 17.5mg of EPA + DHA per 100g, compared with around 10.5mg in grain-fed beef.

Compare this with oily fish, which can provide thousands of milligrams per 140g portion.

So while grass-fed beef can contribute some omega-3 to your diet, it shouldn't be considered a major source of EPA and DHA during pregnancy.

A 2026 update: what's happening with tinned mackerel?

You may have noticed that some tins labelled as mackerel in UK supermarkets are now using jack mackerel.

Some supermarkets, including Sainsbury's, Tesco and Lidl, have changed some products because of concerns around the sustainability of Atlantic mackerel fisheries.

Jack mackerel is a different species from the Atlantic mackerel traditionally used in many UK products.

Different species of fish can have substantially different fatty-acid profiles. At present, there isn't a reliable UK CoFID value that allows us to say exactly how much EPA and DHA is in the Chilean jack mackerel now appearing in some UK products.

So if you're specifically choosing tinned mackerel as a source of omega-3 during pregnancy, check the species listed on the label rather than assuming that every tin labelled "mackerel" has the same nutritional profile.

So, how can I get enough omega-3 during pregnancy?

The good news is that you don't need to make your pregnancy diet complicated.

A practical approach is:

Aim for at least two portions of fish each week, including one portion of oily fish.
Don't worry about buying fresh — frozen and tinned fish can be great options.
Follow the pregnancy fish-safety guidance around oily fish, tuna and high-mercury fish.
If you eat eggs, these can contribute small amounts of DHA, particularly omega-3-enriched eggs.
If you don't eat fish, consider algae-derived omega-3 as an alternative source of DHA.
If you're considering a supplement, choose one suitable for pregnancy and avoid products containing vitamin A/retinol.

And remember: you don't need to hit a perfect number every single day. Looking at your overall diet and regularly including omega-3-rich foods is much more useful than becoming preoccupied with calculating every milligram.

A final thought

Omega-3 is an important part of a healthy pregnancy diet, particularly DHA, which plays an important role in your baby's developing brain and eyes.

The simplest place to start is with your diet.

For most pregnant women, regularly including oily fish within the NHS pregnancy guidance is a practical way to obtain EPA and DHA. If you don't eat fish, there are other options, including omega-3-enriched eggs and algae-derived supplements.

If you're unsure whether you're getting enough omega-3 during pregnancy, particularly if you don't eat fish or have been advised that you are at increased risk of preterm birth, a dietitian, midwife or obstetric team can help you work out what is appropriate for you.

This article is intended for general education and does not replace individual dietetic assessment, medical advice or mental-health care.

References

EFSA Panel on Dietetic Products, Nutrition and Allergies (NDA). Scientific Opinion on Dietary Reference Values for fats, including saturated fatty acids, polyunsaturated fatty acids, monounsaturated fatty acids, trans fatty acids, and cholesterol. EFSA Journal. 2010;8(3):1461. doi:10.2903/j.efsa.2010.1461.

NHS. Fish and shellfish. NHS website.

NHS. Healthy eating in pregnancy. NHS website.

Nogoy KMC, Sun B, Shin S, Lee Y, Zi Li X, Choi SH, Park S. Fatty Acid Composition of Grain- and Grass-Fed Beef and Their Nutritional Value and Health Implication. Food Sci Anim Resour. 2022;42(1):18–33. doi:10.5851/kosfa.2021.e73.

Office for Health Improvement and Disparities. McCance and Widdowson's Composition of Foods Integrated Dataset (CoFID). 2021.

Middleton P, Gomersall JC, Gould JF, Shepherd E, Olsen SF, Makrides M. Omega-3 fatty acid addition during pregnancy. Cochrane Database of Systematic Reviews. 2018;11. doi:10.1002/14651858.CD003402.pub3.

National Institutes of Health, Office of Dietary Supplements. Omega-3 Fatty Acids: Fact Sheet for Health Professionals.