Prenatal exposure to polychlorinated biphenyls: effects on birth size and gestational age.

Polychlorinated biphenyls (PCBs), environmental pollutants that concentrate in the fatty tissue of predatory sports fish, cross the placenta in women exposed to ordinary dietary levels. Two hundred forty-two newborn infants whose mothers consumed moderate quantities of contaminated lake fish and 71 infants whose mothers did not each such fish were examined during the immediate postpartum period. PCB exposure, measured by both contaminated fish consumption and cord serum PCB levels, predicted lower birth weight and smaller head circumference. Exposed infants were 160 to 190 gm lighter than controls, and their heads were 0.6 to 0.7 cm smaller. Head circumference was disproportionately small in relation to both birth weight and gestational age. Control analyses showed that none of these effects was attributable to any of 37 potential confounding variables, including socioeconomic status, maternal age, smoking during pregnancy, and exposure to polybrominated biphenyls. These findings are consistent with earlier reports from studies in laboratory animals.