Terbinafine (Lamisil and Ntilde;) is a synthetic allylamine that is available as both an oral and topical antifungal. It is most commonly prescribed for the treatment of fungal infections of the toenail, fingernail (onchomycosis) and various tineal skin infections. Animal studies on pregnancy exposure revealed no evidence of harm to the fetus. To date, there are currently no well-controlled human studies that assess the safety of terbinafine use in pregnancy. Since August 1996, the manufacturer (Novartis) received a total of 55 spontaneous reports of oral use in pregnant patients. Out of the known outcomes, there were 26 live births, 8 SA's, 6 TA's, 2 congenital abnormalities and 1 neonatal death due to complications in a premature infant. The objective of this study is to evaluate the risk for major malformations and other adverse fetal effects following in utero exposure to terbinafine. Pregnant women who contacted Motherisk inquiring about terbinafine exposures were followed up. The exposed women were compared with 2 groups of women: 1) disease-matched using non-teratogenic antifungals for similar conditions and 2) exposed to non-teratogens. To date, we have completed follow-ups of 54 women gestationally exposed to terbinafine, of these, 26 were exposed to the oral form and 23 to topical. Of the 54 women in this cohort, 24 (45%) were exposed during the first trimester, while the mean duration of exposure to terbinafine was 32 +/- 9.0 days. Pregnancy outcome for exposed group included 50 (92.6%) live births, 3 (5.5%) SA's and 1 (1.9%) TA. One major malformation was noted in among the live births. This is an ongoing study, however, data collected thus far appears to suggest no increased risk for major malformations above baseline risk of 1-3%.