Have you noticed a lot of information about omega-3 during pregnancy and wondered what it actually means for what you put on your plate? Omega-3's are a type of polyunsaturated fatty acid (healthy fat) that is predominantly found in oily fish. The main type of omega-3 that is important during pregnancy is docosahexaenoic acid (DHA) as it helps the baby's eyes and brain development.
Why DHA matters for your baby's development
DHA helps your baby's brain and eyes develop. During pregnancy, your baby draws it from your bloodstream through the placenta, and after birth, from your breast milk. So what you eat directly shapes how much is there for your baby at each stage.1
What you take in supports your baby's brain and eye development, both before and after birth. The brain grows especially fast in the final trimester, so keeping a steady source of DHA going throughout your pregnancy matters, not only in the early weeks.2
Oily fish as your primary source of omega 3 DHA in pregnancy
Oily fish like salmon, sardines, and mackerel are one of the richest food sources of long-chain omega-3, including DHA and EPA. These come ready-made, which means your body can use them straight away without having to convert them first.3
The advice in the UK is to eat no more than two portions of oily fish a week, with one portion being around 140g. The reason for the limit is that oily fish can carry low levels of pollutants like dioxins and polychlorinated biphenyls (PCBs). These can build up in your body and may harm a developing baby in large amounts, which is why a moderate intake is suggested rather than cutting oily fish out completely.4
Plant-based omega 3 sources: ALA, walnuts, and flaxseed
If you do not eat fish, plant-based foods like flaxseeds, walnuts, and chia seeds give you a type of omega-3 called alpha-linolenic acid, or ALA. They are a useful part of a balanced diet, and worth including.6
ALA is not the same as DHA, though. Your body can turn ALA into the long-chain fatty acids EPA and DHA, but only a small amount makes that conversion. So while walnuts and flaxseed add to your overall omega-3 intake, on their own they are not a reliable way to reach the DHA levels that support your baby's brain and eye development.7
Algae oil: the plant-based way to get DHA
Algae oil gives you a plant-based source of ready-made DHA and EPA. Fish build up their omega-3 by eating microalgae, so algae is where these fatty acids start in the food chain. Algae-based supplements provide DHA directly, so your body does not have to rely on that limited conversion from ALA.8
It is also worth knowing that UK guidance advises against fish liver oil supplements during pregnancy. These are different from fish oil or algae oil supplements. Fish liver oil, like cod liver oil, is high in vitamin A (retinol), which can harm a developing baby in large amounts. Algae-based supplements do not carry that vitamin A risk, which makes them a practical option if you do not eat oily fish.9
Putting it together: a practical approach to omega 3 DHA in pregnancy
If you eat fish, up to two portions of oily fish a week within the guidance gives you a direct and reliable source of DHA. If you eat fish now and then but not often, trying to increase the frequency that you include it into your diet and also having a wider range of omega-3 foods such as walnuts and flaxseeds can help meet your requirements. If you do not eat fish at all, leaning on ALA-rich plant foods and talking through an algae-based supplement with your midwife or GP covers both ends of the omega-3 picture.
Whatever your diet looks like, two points hold firm in UK pregnancy guidance here: avoid shark, swordfish, and marlin, and skip fish liver oil supplements. Both apply whatever else you decide about your omega-3 sources.