Research performed in Israel and Europe has found that the new macrolides -- clarithromycin, azithromycin, and roxithromycin -- are not associated with a significantly increased risk of major birth defects or cardiac malformations and in that respect are safe during pregnancy. The data were presented at the 50th Interscience Conference on Antimicrobial Agents and Chemotherapy in Boston. Benjamin Bar-Oz, MD, a neonatologist at the Hadassah University Medical Center in Jerusalem, with colleagues in Italy, Germany, and the Netherlands, conducted a prospective, multinational, multicenter, observational study of 608 women exposed during pregnancy to macrolides (511 of the exposures occured during the first trimester). A control group consisted of 773 women exposed to non-teratogenic preparations during pregnancy. Information was obtained from pregnant women or their healthcare professionals after they contacted their local teratogen information services seeking information after exposure to macrolide drugs. The comparison group included women or their health care professional contacting those centers with questions regarding known non-teratogenic preparations. Information about obstetric and other background parameters was collected at enrollment; after delivery, subjects or their healthcare professionals were contacted to ascertain pregnancy outcome parameters and other exposures through the remainder of pregnancy. According to Dr. Bar-Oz, no significant difference in rates of major birth defects was found between the study group and the comparison group (3.4% vs 2.4%, P=0.36) nor in the rate of cardiovascular malformations (1.6% vs 0.9%, P=0.27). No significant differences were found between subgroups of macrolides in rates of major birth defects or cardiac malformations.