Women who took docosahexaenoic acid supplements to increase fish oil consumption during pregnancy experienced no benefits in terms of postpartum depression or improved cognitive development among their offspring, findings from a study published earlier this week in the Journal of the American Medical Association indicated.

International recommendations suggest that pregnant women increase their consumption of omega-3 polyunsaturated fatty acids, particularly docosahexaenoic acid (DHA), despite the lack of a strong evidence base delineating the supplements’ benefits and risks in this population.

To better determine DHA’s effects, Australian researchers enrolled 2,399 pregnant women in DOMInO, a double-blind, randomized, five-center trial to determine the outcome of increasing DHA intake during the last half of pregnancy.  Participants were assigned to either DHA fish oil supplements (800 mg per day) or vegetable oil capsules.

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Study findings indicated that similar proportions of women in both study groups developed high levels of depressive symptoms in the first six months postpartum (9.67% DHA vs. 11.19% fish oil; adjusted RR=0.85; 95% CI:0.70-1.02; P=.09). Similarly, the researchers observed no differences in mean cognitive composite scores and mean language scores among the 726 study children assessed with the Bayley Scales of Infant and Toddler Development, Third Edition, at 18-month follow-up.

“Our results are at odds with the results of some large-scale epidemiological studies,” the researchers wrote.

They suggested earlier studies indicating that DHA lowered maternal depression rates and improved neurodevelopment in offspring may have overestimated the effect size, and may not have considered residual confounding, or the effect of other beneficial nutrients in fish and seafood.

However, Lisa Stern, APRN, a nurse practitioner at Planned Parenthood in Los Angeles and a Clinical Advisor blog contributor, believes that the benefits of DHA may only fully manifest in the context of other fatty acids, certain nutritional elements and a general healthy life style.

“I would still advise women to continue to find safe, enriching forms of omega-3 fatty acids before, during and after pregnancy,” Stern said. “Potential benefits extend beyond those explored in this study and include maternal health factors, as well as fetal.”

Stern also pointed out the dose of DHA assigned to study participants may have been too small to convey benefits, as previous studies involved DHA supplements of 1 g or more daily – more than the 800 mg dose assigned to DOMInO participants.

Despite the main findings, secondary outcomes from the DOMInO trial indicated that women in the DHA group experienced significantly less preterm births compared with the control group (1.09% vs. 2.25%; adjusted RR=0.49; 95% CI: 0.25-0.94; P=.03), and gave birth to fewer infants with low birth weight (3.41% vs. 5.27%; adjusted RR=0.65; 95% CI:0.44-0.96; P=.03).

In an accompanying editorial, Emily Oken, MD, MPH, of Harvard Medical School and Harvard Pilgrim Health Care Institute, and Mandy B. Belfort, MD, MPH, of Children’s Hospital Boston, advise expecting mothers to adhere to current guidelines, which recommend a daily DHA intake of 200 mg.

Additional studies are needed to determine the specific benefits of DHA supplements for pregnant women and outcomes with higher daily doses.