AbstractA prospective survey was carried out by the French National Institute of Health and Medical Research (INSERM) in 12 University hospitals in Paris and included 12,764 women; 189 gave birth to babies with unequivocal, nonchromosomally based, malformations. There was a significant excess of malformed infants when women had taken phenothiazines during the first three months after the last menstrual period. This association did not seem due to chance or to bias and coud not be explained by the influence of the outcome of previous pregnancies. These data are to be added to results of recent surveys showing a significant increase of malformations in children exposed in utero to anticonvulsants, carbamates, benzodiazepines, tricyclic antidepressants, and amphetamines.