BOSTON, MASSACHUSETTS. Fish is an important source of nutrients required for infant brain development with docosahexaenoic acid (DHA) being especially beneficial. Women are therefore encouraged to increase their fish consumption during pregnancy. With the ever-increasing pollution of fish habitats, including the oceans, the question arises, "Are the benefits of fish consumption outweighed by the risk of mercury contamination?" Researchers at the Harvard Medical School report the results of a study designed to examine the benefits and risks of fish and pregnancy.
Their study involved 135 women and their infants. The women completed semi-quantitative food frequency questionnaires at 26-28 weeks of gestation. The questionnaire was specifically designed to determine the consumption of various types of fish and shellfish. A hair sample was also obtained from the women immediately after delivery. At about 6 months of age the infants underwent a test (VRM) to determine their visual recognition memory, a recognized indicator of infant cognition and brain development. Together, these factors were examined to study the effects of fish and pregnancy.
The average fish consumption during the second trimester was 1.2 servings a week and the mean maternal hair mercury content was 0.55 ppm with 10% of participants having a content above 1.2 ppm. The average VRM score for the infants was 59.8. After adjusting for possible confounding variables, the researchers concluded that a higher fish consumption is associated with a higher VRM score (better cognition), with one additional fish serving a week corresponding to a 4.0 increase in VRM score.
On the other hand, a higher maternal hair mercury content was associated with a significantly lower VRM score (poorer cognition), with a 1ppm increase in mercury corresponding to a decrease of 7.5 in VRM scoring. So is fish and pregnancy safe? The Harvard researchers conclude that women should continue to eat fish during pregnancy, but should choose varieties with low mercury levels.
Oken, E, et al. Maternal fish consumption, hair mercury, and infant cognition in a U.S. cohort. Environmental Health Perspectives, Vol. 113, October 2005, pp. 1376-80