Omega-3 and DHA in Pregnancy: Preterm Birth Trials, Fetal Development and Official Advice
What a large Cochrane review found for omega-3 in pregnancy, including preterm birth, what trials did not show for child development, and what official fish advice says.
Content last updated . This page has not been medically reviewed.
This page uses evidence labels: evidence in a specific group, mixed, insufficient evidence and Proper evidence not found (where we looked and found nothing usable). Study results are about the products tested, not advice.
What the Cochrane review found
| Question | What the review found | How strong |
|---|---|---|
| Preterm birth before 37 weeks | 13.4% with omega-3 versus 11.9% without; risk ratio 0.89 (it is lower with omega-3) [1] | High-quality evidence in the review's grading |
| Early preterm birth before 34 weeks | 4.6% versus 2.7%; risk ratio 0.58 [1] | High-quality evidence |
| Pregnancy going past 42 weeks | Probably increased, from 1.6% to 2.6% [1] | Moderate-quality evidence |
| Large-for-gestational-age babies | A possible small increase [1] | Moderate-quality evidence |
| Pre-eclampsia | May possibly be reduced (risk ratio 0.84, interval 0.69 to 1.01) [1] | Low-quality evidence |
| Child cognition, IQ and vision | Very few differences [1] | Mostly low or very low quality |
The review's authors called omega-3 supplementation in pregnancy an effective strategy for reducing preterm birth, while noting it probably increases the chance of going past term. [1] They also said it is still unclear whether results differ by the type of omega-3, the timing and the amount. [1] That is a real gap: "Proper evidence not found" in this review for which product, timing or amount works best.
Reviews do not always agree. NCCIH, a US National Institutes of Health center, describes a 2016 review of 143 studies in which pregnancies lasted a little longer but there was no effect on the risk of premature birth. [2] It also describes the 2018 Cochrane result above. [2] The sources we read do not explain why the two reviews differ.
Fetal development and later child outcomes
NHS guidance says long-chain omega-3 from oily fish matters in pregnancy because it can help a baby's nervous system develop. [3] That is a statement about eating fish. For supplements, a 2020 review of 15 trials prepared for the US Dietary Guidelines Advisory Committee found limited evidence that omega-3 supplements in pregnancy improve children's cognitive development. [2] NCCIH adds that no benefit was shown for several other mother and infant outcomes. [2] Biomarker changes, such as higher DHA in blood, are not the same as better health for the child.For mood, NCCIH reports a 2019 review in which some studies suggested DHA might reduce depression and anxiety symptoms during pregnancy, but none showed an effect after birth. [2] This is mixed evidence and not a treatment for depression. See omega-3 evidence by use and, if you are struggling, speak to a clinician.
What official advice says
These are the figures we could read. They are not the same kind of advice, so do not compare them directly.| Body, country | What it says | Source and year |
|---|---|---|
| NHS, United Kingdom | Try to eat 2 portions of fish a week, 1 of them oily. When pregnant, avoid more than 2 portions of oily fish a week; avoid shark, swordfish and marlin. Tuna does not count as oily fish. [4][3] | NHS pages, read 2026 |
| FDA and EPA, United States | Pregnancy and breastfeeding: 2 to 3 servings a week from the "Best Choices" list (a serving is 4 ounces), or 1 from the "Good Choices" list [5] | FDA/EPA, content current as of 2024 |
| Dietary Guidelines for Americans, as described by NCCIH | Pregnant or breastfeeding: at least 8 and no more than 12 ounces of a variety of seafood a week, lower in methyl mercury [2] | 2020 to 2025 edition |
| EFSA, European Union | 250 mg a day of EPA plus DHA is an adequate intake for healthy adults and children; the news story we read gives no separate pregnancy figure [6] | EFSA, 2012 |
| Health Canada | Alpha-linolenic acid (ALA, the plant omega-3) adequate intake in pregnancy is 1.4 g a day for ages up to 50; this is ALA, not EPA or DHA [7] | Health Canada, page dated 2025 |
| Perinatal medicine consensus (not a government body) | Pregnant and lactating women should aim for an average of at least 200 mg DHA a day [8] | Koletzko et al., 2008 |
The NIH Office of Dietary Supplements blocked our access, so its figures could not be verified and are not quoted. An EFSA pregnancy-specific DHA figure and a Health Canada EPA plus DHA figure for pregnancy were also not found in the pages we read.
Related
Prenatal multivitamins are covered on prenatal and postnatal vitamins; plant-only diets on omega-3 for vegetarians and vegans; and general pregnancy cautions on pregnancy and breastfeeding safety. Whole-food sources are on oily fish.Frequently asked questions
Does omega-3 prevent preterm birth?
In a 2018 Cochrane review, fewer preterm births occurred among women who received omega-3 than among those who did not (13.4% versus 11.9% before 37 weeks). [1] Another review described by NCCIH found no effect on premature birth risk. [2] It is not a guarantee for any one pregnancy.
Does DHA make a baby smarter?
The sources we read do not show that. A 2020 review found limited evidence for cognitive benefit, and the Cochrane review found very few differences in cognition or IQ. [2][1]
Is fish oil safe in pregnancy?
Side effects are usually mild, but safety depends on the product, your medicines and your allergies. [2] Ask a midwife, doctor or pharmacist first, and ask especially about fish liver oils, which the NHS says are high in vitamin A. [9]
How much fish should I eat while pregnant?
It depends on where you live. The NHS says no more than 2 portions of oily fish a week; the FDA and EPA say 2 to 3 servings a week from their "Best Choices" list. [3][5]
Can I get enough DHA without fish?
Plant foods supply ALA, a different omega-3 from EPA and DHA, and algal oils are a vegetarian DHA source. [2] See the vegetarian and vegan page for the evidence.
More details: evidence, limits and cautions
The details behind this page: cautions, limits of the evidence and where sources disagree. Open any note to read it.
Safety in pregnancy
- Cod liver and other fish liver oils. NCCIH notes these contain vitamins A and D in amounts that vary by product. [2] The NHS says fish liver oil is high in vitamin A, and advises pregnant women to avoid liver and liver products. [9] Read cod liver oil: vitamin A and D content and the pregnancy caution before using any fish liver product.
- Fish choices. The NHS warns that pollutants in oily fish may build up and affect a baby's development, which is why it limits portions. [3] See official fish-eating advice and mercury.
- Medicines and bleeding. The label of a prescription EPA and DHA medicine says omega-3 may prolong bleeding time, and that its pregnancy data were insufficient to identify a risk. [10] Tell your care team about every supplement, and check medication interactions.
- Fish and shellfish allergy. It is not known whether people with these allergies are at higher risk from fish-derived omega-3. [10] See fish allergy and omega-3 products.
- Side effects are usually mild, such as taste, heartburn and diarrhea. [2]
- Quality. Product content and purity vary; see quality testing and certifications.
References
- Middleton P et al. Omega-3 fatty acid addition during pregnancy. Cochrane Database Syst Rev 2018. Read 2026-10-23.
- NCCIH, Omega-3 Supplements: What You Need To Know. Read 2026-10-23.
- NHS, Fish and shellfish: nutrition. Read 2026-10-23.
- NHS, Have a healthy diet in pregnancy. Read 2026-10-23.
- FDA and EPA, Advice about eating fish (content current as of 03/05/2024). Read 2026-10-23.
- European Food Safety Authority, EFSA assesses safety of long-chain omega-3 fatty acids (news story, 27 July 2012). Read 2026-10-23.
- Health Canada, Dietary reference intakes tables: reference values for macronutrients (page dated 2025-11-19, read through a web-fetch summary of the table). Read 2026-10-23.
- Koletzko B et al. The roles of long-chain polyunsaturated fatty acids in pregnancy, lactation and infancy: review of current knowledge and consensus recommendations. J Perinat Med 2008. Read 2026-10-23.
- NHS, Vitamin A. Read 2026-10-23.
- Prescribing information, omega-3-acid ethyl esters capsules (mixed EPA and DHA prescription medicine), DailyMed (revised 11/2024). Read 2026-10-23.