Supplementation with polyunsaturated fatty acids – or omega-3 fatty acids – during pregnancy is an important topic because of unproven claims that polyunsaturated fatty acids (PUFAs) improve fetal brain and eye development if taken during pregnancy, resulting in unnecessary expense for many women who buy these products. In Canada, there are prenatal vitamins available that contain omega-3 fatty acids with a statement that the product "helps support cognitive health and/or brain function" or that omega-3 fatty acids "support "healthy fetal brain and eye development." These are misleading, inappropriate statements, considering that there is no compelling evidence to support these claims.
Claims about the benefits of PUFA supplementation during pregnancy, which have circulated for about a decade, originate from studies that show that when PUFAs are restricted during pregnancy, fetal brain development can be adversely affected, particularly in animals. Other data include several human studies that have linked high cognitive scores to a high seafood content of the maternal diet. The highest levels of PUFAs are measured in the retina, which is part of the visual acuity claim.
My colleagues and I addressed the uncertainties about the benefits of PUFA supplementation in a systematic review of nine randomized controlled trials comparing visual and neurobehavioral outcomes in infants whose mothers received PUFA supplements during gestation with control women who received placebos. Three studies evaluated retinal development and six evaluated neurodevelopment; most ended the supplement at delivery, and evaluations were conducted during the first year, or up to age 2.5, 4, and 7 years in different studies.
Overall, there was no evidence of a beneficial effect of PUFA supplementation during pregnancy on neurodevelopment (IQ, language behaviors) or on visual acuity. As we concluded, there were "very limited, if any" benefits identified, and in the studies with statistically significant differences between the two groups, "the differences were small and of little potential clinical importance" (Obstet. Gynecol. Int. 2012 [doi:10.1155/2012/591531]).
A study published in May 2014 also found no beneficial effect of prenatal supplementation with 800 mg/day of omega-3 fatty acid docosahexaenoic acid (DHA) on neurodevelopmental outcomes in children followed to age 4 years, and the authors concluded that the data "do not support prenatal DHA supplementation to enhance early childhood development." The randomized placebo-controlled study evaluated about 650 children at age 4 years, whose mothers had received the supplement or 333 who received placebo. The mean cognitive scores were not different between the two groups, and the proportion of children with delayed or advanced scores also did not differ between the two groups, nor did other objective assessments of cognition, language, and executive functioning (JAMA 2014;311:1802-4).
Based on the lack of evidence to date, there is no reason to add PUFAs to prenatal vitamins or recommend that women take a PUFA supplement during pregnancy.
The bottom line for clinicians/health care providers is that although the available evidence today has found no detrimental effects of even high doses of omega-3 fatty acid supplementation (up to 3.7 g/day), with the present state of knowledge, there is no evidence that prenatal supplementation with PUFAs improves brain development or acuity of vision in children. Instead of supplementation with PUFA during pregnancy, women should consume a diet with adequate PUFAs, with food that includes eggs and fish, with caution about the mercury content of fish.
Dr. Koren is professor of pediatrics, pharmacology, pharmacy, medicine, and medical genetics at the University of Toronto. He heads the Research Leadership for Better Pharmacotherapy During Pregnancy and Lactation at the Hospital for Sick Children, Toronto, where he is director of the Motherisk Program. He also holds the Ivey Chair in Molecular Toxicology at the department of medicine, University of Western Ontario, London. He had no disclosures relevant to this topic. E-mail him at obnews@frontlinemedcom.com.