Food and Behaviour Research

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Omega‐3 fatty acid addition during pregnancy

Middleton P, Gomersall JC, Gould JF, Shepherd E, Olsen SF, Makrides M (2018) Cochrane Database of Sys Rev  2018, Issue 11.  CD003402. DOI: 10.1002/14651858.CD003402.pub3 

Web URL: Read the abstract and conclusions on here


What is the issue?

Do omega-3 long chain polyunsaturated fatty acids (LCPUFA) taken during pregnancy - either as supplements or as dietary additions in food (such as some types of fish) - improve health outcomes for babies and their mothers? This is an update of a Cochrane Review that was first published in 2006.

Why is this important?

Preterm birth (babies born before 37 weeks pregnancy (gestation)) is a leading cause of disability or death in the first five years of life. Fish and fish oil contain omega-3 LCPUFA (particularly docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA)) and have been associated with longer pregnancies. So it is suggested that additional omega-3 LCPUFAs in pregnancy may reduce the number of babies born preterm and may improve outcomes for children and mothers. However, many pregnant women do not eat fish very often. Encouraging pregnant women to eat fatty fish (which generally have low toxin levels) or to use omega-3 LCPUFA supplements may improve children’s and women's health. This is an update of a Cochrane Review that was first published in 2006.

What evidence did we find?

We searched for evidence in August 2018 and found 70 randomised controlled trials (RCTs; this type of trial provides the most reliable results) (involving 19,927 women). Most trials evaluated a group of women who received omega-3 LCPUFA and compared them with a group of women who received something that looked like omega-3 LCPUFA but did not contain it (placebo) or received no omega-3. The trials were mostly undertaken in upper-middle or high-income countries. Some studies included women at increased risk of preterm birth. The quality of the evidence from the included studies ranged from high to very low; this affected the certainty of the findings for different outcomes.

We found the incidence of preterm birth (before 37 weeks) and very preterm birth (before 34 weeks) was lower in women who received omega-3 LCPUFA compared with no additional omega-3. There were also fewer babies with low birthweight. However, omega-3 LCPUFA probably increased the incidence of pregnancies continuing beyond 42 weeks, although there was no difference identified in induction of labour for post-term pregnancies. The risk of the baby dying or being very sick and going to neonatal intensive care may be lower with omega-3 LCPUFA compared with no omega-3. We did not see any differences between groups for serious adverse events for mothers or in postnatal depression. Very few differences between the omega-3 LCPUFA groups and no omega-3 groups were observed in child development and growth.

Eleven trials reported that they had received industry funding. When we omitted these trials from the main outcomes (such as preterm birth and very preterm birth) it made very little, or no difference, to the results.

What does this mean?

Increasing omega-3 LCPUFA intake during pregnancy, either through supplements or in foods, may reduce the incidence of preterm birth (before 37 weeks and before 34 weeks) and there may be less chance of having a baby with a low birthweight. Women who take omega-3 LCPUFA supplements during pregnancy may also be more likely to have longer pregnancies. More studies are underway and their results will be included in a further update of this review. Future studies could consider if and how outcomes may vary in different populations of women, and could test different ways of increasing omega-3 LCPUFA during pregnancy.


Prematurity and low birthweight increase the risks for all forms of mental health disorder (and many physical health disorders), with effects that are lifelong.

This high-quality systematic review of 70 clinical trials (involving almost 20,000 participants) provides definitive evidence that supplementation in pregnancy with long-chain omega-3 (EPA and DHA) reduces risks for both premature birth and low birthweight.

As the authors of this Cochrane review have actually stated, no further trials are needed of omega-3 vs placebo in pregnancy to address this basic question of whether omega-3 can reducing pre-term birth, as the benefits have now been clearly established. 

However, further studies could help to determine which sub-populations show most benefit from additional omega-3, and the best ways to deliver this by supplementation to mothers-to-be who may be unable or unwilling to consume enough EPA/DHA from fish and seafood (which is the main dietary source of these essential brain fats, and also provides other key nutrients importat for brain development, such such as iodine, zinc, Vitamn D, choline and B vitamins). 

Trials from both the US and Australia have already shown that omega-3 supplementation during pregnancy would be cost-effective based purely on the short-term savings in immediate hospital costs alone.  Longer-term follow-up studies could provide a more comprehensive assessment of benefits vs costs, but would obviously involve not only cost and practical obstacles, but also ethical cosiderations now that the benefits of omega-3 for reducing preterm birth have been so clearly established.

See the associated news article:

An earlier version of this Cochrane review, from 2008, can be found here.  And re possible mechanisms explaining how omega-3 help to prevent preterm birth, see:

For more information on this topic, see also the following lists of articles, which are regularly updated: