Antiviral prophylaxis cuts herpes risk at birth. (Lesions in 5% on Acyclovir, 15% on Placebo).

WHISTLER, B.C. -- Antiviral treatment in the last trimester for women with recurrent herpes genitalia reduces by two-thirds their chance of developing lesions at the time of delivery, Dr. Deborah M. Money said at an update on viral infections sponsored by the University of British Columbia.

In a study of 170 pregnant women with recurrent herpes randomized to either 400 mg of acyclovir three times daily or placebo from 36 weeks to delivery, 15% of patients on placebo and 5% on acyclovir developed a lesion at the time of delivery, said Dr. Money, associate director of STD/HIV control for the British Columbia Centre for Disease Control in Vancouver.

"Based on our data, it seems very reasonable to go with antiviral therapy near the end of pregnancy," she said. "We're suggesting acyclovir, because that is what we are familiar with."

The practice of treating patients with recurrent herpes as a way to help avoid a cesarean section has become fairly widespread. However, previous studies that have supported this strategy have had some shortcomings, Dr. Money said.

One study published last year showed that treatment reduced the likelihood of an infected mother having a cesarean from 16% to 8%. However, that study compared women who were treated with acyclovir with those who received no treatment and therefore was not blinded to the obstetricians attending the delivery.

The current study used polymerase chain reaction testing to detect virus shedding, unlike previous studies that used culture, which is less sensitive for detecting the virus. The study showed that the proportion of women shedding virus during the treatment period was reduced from 40% in the placebo group to 11% in the treated group.

More importantly 19% of women in the placebo group but only 6% of the ...