Role of Omega-3 Fatty Acids in Maternal, Fetal, Infant and Child Wellbeing

Ellen Mozurkewich; Deborah R Berman; Julie Chilimigras


Expert Rev of Obstet Gynecol. 2010;5(1):125-138. 

In This Article

Safety Considerations in Use of Supplements

Fish oil supplementation up to doses of 3 g/day during pregnancy has not been associated with any increase in adverse outcomes in randomized, controlled trials.[45] There is some evidence that omega-3 fatty acids have the potential to exert a mild antithrombotic effect; however, the risk of bleeding is very small, even when supplements are administered with other agents that increase bleeding, such as aspirin, heparin and warfarin.[99] A recent Cochrane review of randomized, controlled trials of marine oil supplementation in pregnancy evaluated the risk of antepartum bleeding and bleeding at delivery, and did not note any significant difference in these complications between women who received supplements and women receiving placebo.[45]

Likewise, omega-3 fatty acid supplementation might theoretically pose a risk for increased post-term gestations. Although the Cochrane review reporting this outcome noted a trend toward more post-term gestations in supplemented pregnancies, this difference was not statistically significant.[45] As noted previously, although several observational studies have raised concern regarding reduced fetal growth in pregnancies among women with the highest levels of dietary fish consumption or high consumption of cod liver oil early in pregnancy,[49,55] there have been no beneficial or harmful effects on these outcomes among fish oil-supplemented women in the randomized, controlled trials, suggesting that these risks may result from industrial contaminants in fish or other components of cod liver oil.[45] It is also possible that there is a U-shaped dose–response curve for omega-3 fatty acid intake, with moderate intake being optimal for health and development, and high intake causing increased risk.

Fish oils are susceptible to oxidation, which contributes to patient intolerance.[99] Some women taking fatty acid supplementation in clinical trials have complained of belching and fishy aftertaste, posing problems for compliance and blinding.[100] Refrigerating fish oil supplements prior to administration appears to reduce fishy aftertaste and improve tolerance.[99] Most intolerances, including potential toxicities and fishy smell and taste, can be reduced during the purification process used by the manufacturer.[99]

Overall, the totality of evidence suggests that the benefits of fish intake generally exceed the potential risks for women of childbearing age, as long as the few high-toxin fish species (shark, swordfish, king mackerel and tilefish) are avoided.[101] Although fish oil supplementation poses a theoretical risk for exposure to industrial contaminants, such as mercury, dioxin and polychlorinated biphenyls, this risk is well below the risk posed by eating fish, and in adequately purified fish oil supplements, contaminant exposure is zero to negligible.[99] Therefore, fish oil supplements may be the preferred therapeutic source of omega-3 fatty acids.[99]


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