Information on 1475 mothers of infants with selected structural malformations and an equal number of mothers of "normal" babies was analyzed for a possible relationship between shift work and adverse pregnancy outcome or a complicated course of pregnancy. The primary data were obtained from the Finnish Register of Congenital Malformations supplemented by special interviews on the mothers' work conditions. No signs of a teratogenic risk were observed. The relationship between course of pregnancy and outcomes other than malformations was determined from the noncase mothers' experience. Threatened abortion and pregnancy-induced hypertension were not associated with rotating shift work alone, but in a noisy work environment moderate risks could not be ruled out. Rotating shift work was associated with a slight excess of babies small for their gestational age independently of noise exposure. The results suggest that further studies on the effects of different work schedules on pregnancy are worth consideration.