Is High Consumption of Fatty Fish During Pregnancy a Risk Factor for Fetal Growth Retardation? A Study of 44,824 Danish Pregnant Women

Abstract

Observational studies point to a positive association between fish consumption and both birth weight and prolonged gestation. Prolonged gestation has been associated with marine n-3 fatty acids, in particular, eicosapentaenoic acid and docosahexaenoic acid, in several—but not all—randomized controlled trials. The present study examined the relationship between fetal growth and fish consumption during pregnancy in 44,824 women from the Danish National Birth Cohort, enrolled during the years 1996–2002. The cohort included about 30% of all deliveries taking place in Denmark during this period. Consumption of total, fatty, and lean fish was estimated by a food frequency questionnaire in mid-pregnancy. Birth rates of infants who were below the 10th percentile for gender and gestational age were significantly increased for women consuming more than 60 g of fish on a daily basis compared with those taking 5 g or less. The adjusted odds ratio was 1.24 (95% confidence interval [CI], 1.03–1.49) for birth weight and 1.21 (95% CI, 1.01–1.43) for head circumference. The adjusted odds ratio for birth length was of borderline significance. Associations with total fish consumption were accounted for entirely by the consumption of fatty fish. Women who ate fatty fish at least 4 times per month were significantly more likely than others to give birth to small-for-gestational-age children. Consumption of lean fish was not associated with any adverse birth outcome. The risk of fetal growth restriction in the offspring of women who reported heavy maternal fish consumption in this large cohort study was increased approximately 24%. However, almost all this increased risk was associated with fatty fish consumption, and thus may be due to exposure to persistent organic pollutants. The investigators suggest that pregnant women be encouraged to consume moderate amounts of fatty fish.