--- title: 'Omega 3 and DHA in Pregnancy: Why They Matter and Where to Find Them' slug: omega-3-dha-pregnancy-what-to-eat lifeStage: pregnancy category: Nutrition medicalReviewer: 'Sophie Mumby, Registered Dietitian' reviewerId: 'https://blog.bloume.com/pregnancy/medical-board.md#sophie-mumby' lastUpdated: '2026-08-11' primarySource: 'Understanding LCPs: DHA in pregnancy' wordCount: 1065 readTimeInSeconds: 266.25 --- # Omega 3 and DHA in Pregnancy: Why They Matter and Where to Find Them Docosahexaenoic acid (DHA), a long-chain omega-3, helps build your baby's brain and eyes during pregnancy. Oily fish like salmon, sardines, and mackerel are the most direct food source, though UK guidance suggests a limit of two portions a week. If you do not eat fish, plant-based options like walnuts, flaxseeds, and algae-based supplements can help support your intake. This article covers the key food sources, portion guidance, and what to know about plant-based alternatives. **Q: How much oily fish can you eat in pregnancy?** A: UK guidance suggests no more than two portions of oily fish a week in pregnancy, with one portion being around 140g. Oily fish like salmon, sardines, and mackerel are encouraged within that limit because they give you DHA directly. Going over two portions a week is not advised, as pollutants like dioxins and PCBs can build up over time. 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. 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. ## 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. 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. > **WARNING**: If you are pregnant or trying to get pregnant, it is best to avoid shark, swordfish, and marlin completely. These can carry higher levels of mercury than other fish, which can harm a developing baby's nervous system. This applies no matter how much you eat. ## 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. 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. ## 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. 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. > **INFO**: UK guidance takes a food-first approach to omega-3 in pregnancy, with oily fish within the recommended limit as the main source. Omega-3 supplements are not recommended for everyone in pregnancy. If you are thinking about an algae-based or any other omega-3 supplement, it is worth speaking to your midwife or GP before you start. ## 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. --- **Q: How much oily fish can you eat in pregnancy?** UK guidance suggests no more than two portions of oily fish a week in pregnancy, with one portion being around 140g. Oily fish like salmon, sardines, and mackerel are encouraged within that limit because they give you DHA directly. Going over two portions a week is not advised, as pollutants like dioxins and PCBs can build up over time. **Q: Which fish should you avoid completely in pregnancy?** It is best to avoid shark, swordfish, and marlin completely in pregnancy and when you are trying to conceive. These can carry higher levels of mercury than other fish, which can harm a developing baby's nervous system. This applies whatever the portion size. **Q: Can you get enough DHA from plant-based foods alone?** Plant-based foods like walnuts, flaxseeds, and chia seeds give you ALA, a type of omega-3 your body can turn into DHA. Only a small amount converts, though, so plant foods on their own are not a reliable way to meet your DHA needs in pregnancy. Algae-based supplements give you ready-made DHA directly and are a practical option if you do not eat oily fish. It is worth speaking to your midwife or GP before starting any supplement in pregnancy. **Q: Is it safe to take fish oil supplements in pregnancy?** Standard fish oil supplements are different from fish liver oil supplements like cod liver oil. UK guidance specifically advises against fish liver oil in pregnancy because it is high in vitamin A (retinol), which can harm a developing baby. If you are weighing up any omega-3 supplement in pregnancy, including fish oil or algae oil, it is worth talking it through with your midwife or GP first. Omega-3 supplements are not recommended for everyone in pregnancy in the UK. ### Clinical Sources - [Understanding LCPs: DHA in pregnancy](https://www.aptaclub.co.uk/pregnancy/diet-and-nutrition/key-vitamins-and-nutrients/understanding-lcps.html) - [Understanding LCPs: DHA in pregnancy](https://www.aptaclub.co.uk/pregnancy/diet-and-nutrition/key-vitamins-and-nutrients/understanding-lcps.html) - [Fish and Omega-3 - NHS](https://www.nhs.uk/live-well/eat-well/food-types/fish-and-shellfish-nutrition/) - [NHS: Foods to avoid in pregnancy](https://www.nhs.uk/pregnancy/keeping-well/foods-to-avoid/) - [NHS: Foods to avoid in pregnancy](https://www.nhs.uk/pregnancy/keeping-well/foods-to-avoid/) - [It's common for women to develop iron deficiency during pregnancy](https://www.nutrition.org.uk/nutrition-for/pregnancy/) - [Omega-3 Fatty Acids, DPA, DHA and their Role in Human Health](https://pmc.ncbi.nlm.nih.gov/articles/PMC7759779/) - [A Guide to Algae Oil Omega-3](https://www.boltpharmacy.co.uk/guide/algae-oil-omega-3) - [NHS: Foods to avoid in pregnancy](https://www.nhs.uk/pregnancy/keeping-well/foods-to-avoid/) - [NICE NG247: Postnatal care](https://www.nice.org.uk/guidance/ng247) --- Reviewed by Sophie Mumby, Registered Dietitian | [Medical Board](https://blog.bloume.com/pregnancy/medical-board.md) | August 2026