Exposure to environmental tobacco smoke in nonsmoking pregnant women in relation to birth weight.

The objective of this study was to determine whether birth weight is related to maternal exposure to environmental tobacco smoke. A cohort study was conducted in a sample of 710 nonsmoking women attending a prenatal education program in the third trimester of pregnancy in La Fe Hospital, Valencia, Spain. The duration of exposure to environmental tobacco smoke in the home, at work, and in vehicles and public places was collected by structured questionnaire. Cotinine levels were determined in saliva samples. Multiple regression was used to control for infant's sex and gestational age and for maternal age, height, prepregnancy weight, parity, education, social class, and episodic illnesses during pregnancy. The mean birth weight of infants of women with cotinine levels > 1.7 ng/ml was 87.3 g lower than that of infants of women with cotinine levels in the range 0-0.5 ng/ml (p = 0.048). Birth weight was negatively associated with average weekly duration of exposure in public places (p < 0.05), whereas mothers exposed to the partner's smoke for up to 14 hours/week had infants 177.2 g heavier than those of unexposed mothers. Although the evidence is weak for an effect of exposure to environmental tobacco smoke on the fetus of nonsmoking pregnant women, it may be sufficient to recommend restriction of smoking in enclosed work-and public places to reduce any risk of growth retardation.