The widespread use of hormonal contraceptives for a prolonged time in women during the child-bearing period necessitates that appropriate precautions be taken to ensure safety for the patient as well as for her progeny. Hormonal administration during or prior to pregnancy may be potentially teratogenic. Although there have been many reports during the last decade, it has been very difficult to document conclusively such a relationship. Over-all, it seems that hormonal use prior to pregnancy does not lead to an increase in the frequency of chromosomal aberrations or of congenital malformations. The use of certain hormones during pregnancy, on the other hand, may lead to an increase in the incidence of congenital malformations, probably in the genetically predisposed fetus. In view of this concept hormonal contraceptives should not be used to treat threatened abortion, and their use as a pregnancy test should be abandoned. Since the question of the safety of the inadvertent administration of pills during early pregnancy has not been resolved, the mother should be informed of the potential risks.