Adverse pregnancy outcome in women exposed to acyclovir during pregnancy: a population-based observational study.

This study aimed to examine the risk of adverse pregnancy outcomes in children born to mothers who redeemed a prescription for systemic or topical acyclovir during pregnancy. Data on prescriptions of acyclovir were obtained from the Danish North Jutland Prescription Database and data on pregnancy outcomes from the Danish Medical Birth Registry and the County Hospital Discharge Registry. The risk of malformations, low birth weight, preterm birth and stillbirth in users of acyclovir were compared with non-exposed women using a follow-up design, while the risk of spontaneous abortion was examined using a case-control design. 90 pregnant women had redeemed a prescription for systemic acyclovir, and 995 women for topical acyclovir, during 30 d before conception, or during their pregnancies from 1 January 1990 to 31 December 2001. The odds ratios (95% confidence intervals) of the exposed relative to the non-exposed for the systemic and topical acyclovir were: malformations, 0.69 (0.17-2.82) and 0.84 (0.51, 1.39); low birth weight, 2.03 (0.50-8.35) and 0.48 (0.21-1.07); preterm birth, 1.04 (0.38-2.85) and 0.95 (0.70-1.28); stillbirth (for topical acyclovir), 1.70 (0.80-3.60); and spontaneous abortion, 2.16 (0.60-7.80) and 1.29 (0.80-3.60). There is increasing evidence that the use of systemic acyclovir is not associated with an increased prevalence of malformations at birth and preterm delivery. The data for low birth weight and spontaneous abortion are still inconclusive, although the risk of spontaneous abortion is increased in women exposed to acyclovir during the first month of pregnancy. The use of topical acyclovir does not seem to be associated with any adverse pregnancy outcome, although data on stillbirth are inconclusive.