A new study published on Oct 20 in the Journal of American Medical Association suggests taking fish oil or DHA supplements during the second half of pregnancy may not reduce risk of postnatal or postpartum depression.

The study also suggests that such a supplementation may not help new born babies in the development of their cognitive capability and language skills.

The study was conducted by Maria Makrides from Child Nutrition Research Centre, Women's and Children's Hospital, Flinders Medical Centre, and Women's and Children's Health Research Institute in Adelaide, Australia and colleagues.

The research involved 2389 women who were less than 21 weeks' gestation with singleton pregnancies who were assigned to receive either 800 mg per day of docosahexaenoic acid (DHA) or vegetable oil capsules during the last half of their pregnancies and 60 days after birth.

The participating women were assessed for high levels of depressive symptoms at 6 weeks and 6 months and children assessed at 18 months for their cognitive and language development.

The researchers found high levels of depressive symptoms were found in 9.67 percent of the DHA supplemented women and 11.19 percent of controls during the first 6 months postpartum, a 15 percent difference, which was ultimately considered insignificant.

Cognitive composite scores and language composite scores did not differ in the two groups, the researchers said.

The trial report was released at http://jama.ama-assn.org/cgi/content/full/304/15/1675

One industry organization suggests that the trial was not reliable since the initial DHA levels in the subjects were not measured. There is a possibility that the participants had already had high levels of DHA in their systems.  But the researchers said during the trial, DHA levels without supplementation should be low.

A health observer pointed out that the trial did not consider other risk factors which could compromise the trial results.

For instance, vitamin D has been found an important determinant for depression in women and for children's brain development.  With this single important factor uncontrolled, it is hard to say that fish oil is useless as indicated in the current study.

Fish oil high in omega-3 fatty acids has been found associated with a myriad of health benefits.  High quality fish oil or DHA has been enlisted by some people as an anticancer agent, among other things.