Taking fish oil supplements while pregnant does not decrease a woman's risk of depression after giving birth, and, contrary to some previous studies, does not improve her child's cognitive or language development, a new study from Australia suggests.

Pregnant women who took supplements of docosahexaenoic acid (DHA), one of the omega-3 fatty acids found in fish oil , developed post-partum depression at about the same rate as women who didn't, the researchers found.

Furthermore, their children didn't score any higher on cognitive or language tests.

"Our data suggest that there is no need [for] apparently healthy pregnant women to take DHA supplements," said Maria Makrides, deputy director of the Women's and Children's Health Research Institute, based in North Adelaide.

The results of the study, which involved 2,399 Australian women, appears tomorrow (Oct. 20) in the Journal of the American Medical Association.

No difference in results

The volunteers were no more than 21 weeks pregnant when the study began.
Some of them were given DHA-rich fish oil supplements, and the others were given placebo vegetable oil tablets.

Among the women who took the fish oil, 9.7 percent developed depression within six months after the delivery, while 11.2 percent of those who took the placebo did, the study said. The difference was small and could have been due to chance, Makrides said.

The researchers then tested skills of the women's babies when the children were 18 months old. Cognitive, language and motor development scores didn't differ between the children of the women who took the supplements and the children of the women who took the placebo, the researchers said.

That finding seems to contradict a number of observational studies that found improved abilities among the children of moms who took fish oil. A 2003 study in the journal Pediatrics showed higher mental-processing test scores in those children, and a small 2008 study in the journal Archives of Disease in Childhood: Fetal and Neonatal Edition found better hand-eye coordination.

Makrides told MyHealth NewsDaily that past studies may have overestimated the effect of DHA, and that nutrients or compounds in seafood beside DHA may be providing the beneficial health effects.

The findings don't mean women should give up taking fish oil.

It has been linked to a decreased risk of breast cancer, according to a July article in the journal Cancer Epidemiology, Biomarkers & Prevention.

And Makrides said that there's evidence fish oil improves circulation, lowers blood pressure and reduces inflammation in stiff joints.

Post-term births

The Australian researchers also found women who took the fish oil supplements lowered the risk of having a pre-term baby (born before 34 weeks of pregnancy). However, they raised the risk of going past their due date, and requiring a Caesarian section or labor induction.

For every 100 women given DHA supplements, on average, one woman would be spared from a pre-term birth, but two women would need post-term induction or a C-section, Makrides said.

"These trade-offs are important to consider, and it may be that DHA supplementation may be most useful to women at risk of having a pre-term baby," she said.

Because of this benefit, pregnant women should still take the doctor-recommended 200 milligrams of DHA a day, said Dr. Emily Oken, of the Harvard Pilgrim Health Care Institute, and Dr. Mandy B. Belfort, of Children's Hospital Boston, who wrote an editorial that accompanied the study.

Makrides said she hopes next to investigate whether DHA can help women with a history of depression or women with a high risk of delivering a premature baby . She also plans to do a four-year follow-up of the children who were tested at 18 months.