Pregnant women who take DHA fish oil capsules during pregnancy do not reduce their risk of developing post-natal depression, nor do the supplements have any effect on the baby’s cognitive and language development during early childhood, researchers from the Women’s and Children’s Health Research Institute, Adelaide, Australia, reported in an article published in the medical journal JAMA (Journal of the American Medical Association). Dietary docosahexaenoic acid (DHA) is often recommended to pregnant women as a way of enhancing their offspring’s intelligence as well as protecting from subsequent post-natal depression (postpartum depression). In fact, previous studies have suggested so.

The authors wrote:

Epidemiological investigations from the United States and Europe demonstrate that higher intakes of n-3 long-chain polyunsaturated fatty acids (LCPUFA) from fish and seafood during pregnancy are associated with a reduced risk of depressive symptoms in the postnatal period, as well as improved developmental outcomes in the offspring. However, n-3 LCPUFA intervention trials in human pregnancy have reported mixed results and have not been conclusive largely because of methodological limitations.

Apparently, previous trials which looked at cognitive and language development outcomes in children were small and had high drop-out rates.

The investigators add:

Despite the paucity of evidence, recommendations exist to increase intake of DHA in pregnancy, and the nutritional supplement industry successfully markets prenatal supplements with DHA to optimize brain function of mother and infant. Before DHA supplementation in pregnancy becomes widespread, it is important to know not only if there are benefits, but also of any risks for either the mother or child.

Maria Makrides, B.Sc., B.N.D., Ph.D. and team carried out a randomized, multi-center trial to determine whether DHA fish oil supplements during the latter half of pregnancy had any effect on the risk of developing postpartum depression, as well as enhancing cognitive development of the baby during their first years. 2,399 females less than 21-weeks pregnant were recruited at 5 maternity hospitals in Australia between October 2005 and January 2008. By the end of December 2009 a total of 726 children were followed-up. The pregnant women had received 800 mg/d of DHA fish oil capsules or equivalent vegetable oil capsules with no DHA up to the day of childbirth. 96.7% of the women completed the course of capsules.

The Edinburgh Postnatal Depression Scale was used to gauge levels of maternal depression, and the Bayley Scales of Infant and Toddler Development were utilized to measure cognitive and language development of the offspring.

9.67% of the DHA group and 11.19% of the control (vegetable non DHA capsules) group reported high levels of depressive symptoms – not a significant difference. There was no significant difference between either group regarding a new medical diagnosis for depression during the trial, or diagnosis requiring treatment (while taking the capsules).

The children’s cognitive scores were the same in both groups as were language development scores. Measurements of motor development and social-emotional behavior were similar in both groups.

The researchers wrote:

Current recommendations suggest that pregnant women increase their dietary DHA to improve their health outcomes as well as those of their children. Such recommendations are increasingly being adopted with women taking prenatal supplements with DHA. However, the results of [this trial] do not support routine DHA supplementation for pregnant women to reduce depressive symptoms or to improve cognitive or language outcomes in early childhood.

Our results are at odds with the results of some large-scale epidemiological studies. It may be that even well-conducted epidemiological studies overestimate effect size and do not adequately deal with residual confounding, or that other nutrients in fish and seafood, beyond DHA, contribute to the observations from epidemiological studies. Further studies are required to determine whether there are specific benefits of DHA supplementation for women with a previous history of depression and for women at risk of preterm birth.

Emily Oken, M.D., M.P.H., of Harvard Medical School and Harvard Pilgrim Health Care Institute, and Mandy B. Belfort, M.D., M.P.H., of Children’s Hospital Boston, wrote:

Fish oil supplements are safe, well tolerated, and reduce risks for early preterm birth, which is associated with poor neurocognitive outcomes and maternal depression. Whether fish consumption during pregnancy will confer similar or perhaps even greater benefits for mothers and their children requires more investigation, including large randomized trials such as [this trial]. For now, pregnant women should take care to get the recommended intake of 200 mg/d of DHA, either by including low-mercury, high-DHA fish in their diets or by taking a daily n-3 PUFA supplement. The benefit of higher intakes remains unclear.

“Effect of DHA Supplementation During Pregnancy on Maternal Depression and Neurodevelopment of Young Children – A Randomized Controlled Trial”
Maria Makrides, BSc, BND, PhD; Robert A. Gibson, BSc, PhD; Andrew J. McPhee, MBBS; Lisa Yelland, BSc; Julie Quinlivan, MBBS, PhD; Philip Ryan, MBBS, BSc; and the DOMInO Investigative Team
JAMA. 2010;304(15):1675-1683. doi:10.1001/jama.2010.1507

Written by Christian Nordqvist