In this paper in Pediatrics, the authors randomized women to two treatment groups. One group of women supplemented their diet with corn oil (the control group) and the other group took cod liver oil .. which is high in docosahexaenoic acid (DHA; 22:6 n-3) and arachidonic acid. With a large increase in the cerebral content of these compounds during the 3rd trimester of pregnancy, the authors hypothesized that maternal intake of DHA during pregnancy and lactation was marginal and that high intake of this fatty acid would benefit children.
The results of this small study were interesting enough to report to our pregnant patients — but not compelling enough for me to suggest that 10cc of doc liver oil be taken every day for the 3rd trimester and the 1st 3 months of breastfeeding. Kids whose moms got the cod liver oil did score better on an intelligence test (and had bigger heads at birth). Nonetheless, there is minimal risk, and there does appear to be benefit. AS the authors mention:
"The difference of 4.1 points in the scores on the Mental Processing Composite of the K-ABC between the 2 groups may have limited significance on individual basis but may be of epidemiologic importance. Didactic procedures increasing IQ with 4 points among school children, with no harmful side effects, would immediately be implemented in schools."