Recent studies have shown that a course of antiviral therapy for human immunodeficiency virus (HIV) infection early in a pregnancy can reduce the rate of perinatal transmission of the disease. The exact mechanism for this reduction is unclear, and there is scant information about the impact of short courses of antiviral therapy given late term. Chuachoowong and colleagues studied HIV levels in cervicovaginal lavage and plasma samples in relation to perinatal transmission risk of HIV after a short course of zidovudine.

The study consisted of 397 pregnant women who were HIV positive. The women were randomized into a treatment and placebo group. The treatment group received 300 mg of zidovudine twice daily starting at 36 weeks of gestation. They also received 300 mg every three hours while in labor until delivery. Serum studies for HIV were performed at baseline, 38 weeks of gestation and delivery. Cervicovaginal lavage samples were collected at 38 weeks of gestation. The serum and lavage samples were evaluated for HIV RNA levels. The infants delivered were also tested to determine transmission rates.

There was a significant reduction in the cervicovaginal lavage HIV RNA levels between the treatment and placebo groups. There was also an association between the HIV RNA levels in the cervicovaginal lavage sample and the perinatal transmission rate. Treatment with a short course of zidovudine decreased the HIV RNA levels in the cervicovaginal sample and reduced HIV perinatal transmission.

The authors conclude that even a short course of an antiviral agent can reduce the risk for perinatal transmission of HIV in pregnant women with the virus. They also conclude that the cervicovaginal lavage sample provided a better correlation of the risk of transmission than serum samples. Exposure of the infant to HIV in the cervicovaginal secretions should be minimized to reduce the risk of transmission.