A case-control study of paternal smoking and birth defects.

Although the influence of paternal smoking on birth defects is of great public interest, epidemiological evidence concerning this potential relationship is extremely limited. A stratified random sample of 29 hospitals in the Shanghai Municipality, China, was used to select 1012 birth defects cases and controls. Mothers of the cases and controls were interviewed in the hospitals from October 1986 to September 1987. A modest relationship between paternal smoking and overall birth defects in offspring was identified [odds ratio (OR) = 1.21, 95% confidence interval (CI): 1.01-1.45]. More markedly elevated risks were identified for anencephalus (OR = 2.1), spina bifida (OR = 1.9), pigmentary anomalies of the skin (OR = 3.3) and varus/valgus deformities of the feet (OR = 1.8). Our analysis also shows that paternal smoking is more likely to be associated with multiple rather than isolated malformations. A paternally-mediated effect of smoking on birth defects is suggested and further studies are encouraged.