Although only 5 to 10 percent of women of reproductive age in the United States report having clinical genital herpes infection (HSV), up to 30 percent have antibody evidence of infection and risk transmitting the infection to their infants during delivery. Current policies to limit neonatal transmission focus on cesarean delivery for women who have symptoms near term. However, because of the large number of asymptomatic carriers, more than 70 percent of neonatal HSV cases occur in children born to women without obvious HSV infection. Sheffield and colleagues reviewed the evidence for effective prophylaxis therapy with acyclovir during the last month of pregnancy.

The authors searched electronic databases, conference proceedings, bibliographies, and registries of trials for prospective, randomized controlled trials of acyclovir in pregnant women with HSV infection. If necessary, authors were contacted for nonpublished data pertinent to the meta-analysis. From the original 22 identified studies, only five met inclusion criteria for methodologic quality. These five studies involved 799 pregnant women.

The combined results of the studies showed a significant reduction in clinical HSV transmission at delivery, regardless of the dosage of acyclovir. Overall, the rate of recurrence was 4 percent in patients receiving treatment compared with 15 percent in the placebo group. Patients receiving acyclovir also were significantly less likely to undergo cesarean delivery. In four studies, viral culture was used at delivery to detect HSV. None of the 339 patients who received acyclovir antenatally had HSV detected at delivery compared with 15 (5 percent) of the 293 patients who received placebo. No cases of neonatal HSV occurred in the 799 deliveries.

The authors concluded that the type of HSV did not influence the results. They also examined the effect of different dosages of acyclovir. The odds ratio for HSV recurrence at delivery was 0.13 in two studies using 800 mg of acyclovir per day. When 1,200 mg of acyclovir was used, the odds ratio of 0.34 was just statistically significantly improved. For HSV detection at delivery, the odds ratio for treatment with 1,200 mg was not significantly better than that for 800 mg (0.13 compared with 0.09).

The authors conclude that prophylactic acyclovir therapy from the 36th week of pregnancy reduces the risks of clinical HSV in the mother at delivery, cesarean delivery, and asymptomatic viral shedding at delivery. Similar results were noticed regardless of type of HSV disease and dosage of acyclovir.