Aims: Polychlorinated biphenyls (PCBs), environmental pollutants that concentrate in fatty tissue in humans, cross the placenta. Infants born from occupationally or accidentally exposed mothers to high PCB levels, had lower birth weights. The Netherlands belong to countries with highest background PCB levels. Therefore we studied birth size in Dutch newborns.

Methods: In 1990-1992, 207 mother-infant pairs were recruited. Infants, 1st or 2nd, born at term (37-42 wks of gestation), caucasian, without perinatal complications, were included, Birth weight (BW) was measured at birth and crown-heel (CH) length within 2 weeks after birth. In utero exposure to PCBs was estimated from cord plasma PCB levels. Confounding variables on birth size, e.g. smoking and alcohol use during pregnancy, parity, gender of the child, target height and gestational age (GA) were obtained by parental interview. Linear regression analysis was performed in 179 respectively 159 infants for BW and CH length as outcome variables.

Results: Mean (SD) of BW and CH length were 3458 (459) g and 51.4(19) cm respectively. Median (range) cord plasma PCB levels were 0.40(0.08-2.08) μ/l, Multiple regression analysis showed that, after adjustment for covariates, BW was significantly negatively associated with cord plasma PCB levels (p=0.026, R2=0.33). CH-length was not significantly related to cord plasma PCB levels. Alcohol use and smoking during pregnancy, GA, gender, parity and target height were also significantly associated with birth weight and CH-lenght.

Conclusions: There is a significant negative association between cord plasma PCB levels and birth weight in Dutch newborns. Although the negative effect of intra uterine exposure to background PCB levels on birth weight is small, its magnitude is greater than smoking.