In about 80% of all pregnant women medical drugs are used during pregnancy. Phytomedicines play an important role in self- and prescribed medication. Since the thalidomide tragedy teratogenic effects of medicamentous treatment are well known. Only a few investigations and studies on the tolerability and safety of plant-based medicines in pregnancy have been published. From 1992-1997 a nationwide retrospective surveillance study of 762 pregnant women (786 newborns) was conducted to evaluate the safety of the herbal combination preparation Sinupret during pregnancy. Standardized questionnaires were used for retrospective and systematic examination of all pregnancies. All cases were treated with Sinupret for at least 24 hours. The data of the population-based Mainz birth registry were used for comparison, interpretation and evaluation of the Sinupret study. For infants with birth defects and/or clinically abnormal pregnancies single-case-analyses were performed. The study collective was representative for Germany. 13 single-case-analyses were performed. In three cases the pregnancy ended with an abortion and in one case with an intrauterine death of the fetus. Nine newborns (1.1%) were diagnosed with major malformations. The critical evaluation of the collective and the individual cases yielded no evidence of possible teratogenic and/or embryotoxic effects of the phytomedicine in 11 out of 13 cases. In the remaining two cases a causal relationship is theoretically possible but very unlikely. On the whole the study underlines the value of the pediatric epidemiologic research in malformations of the Mainz birth register for the monitoring, assessment and evaluation of pharmaceutical studies on drug safety during pregnancy.