Background: The Pediatric AIDS Clinical Trials Group Protocol 076 reported a reduction in the rate of perinatal transmission of the human immunodeficiency virus (HIV) from 25.5 percent to 8.3 percent with a three-part regimen of zidovudine given ante partum, intra partum, and to the newborn. We examined the effects of abbreviated zidovudine regimens on perinatal HIV transmission using data from the HIV polymerase-chain-reaction (PCR) testing service of the New York State Department of Health. Pregnant women who received abbreviated regimens rather than the recommended regimens did so because of limited prenatal care or by choice.

Methods: The requisition form used by the PCR testing service included information on the demographic characteristics of the infants and the timing of any perinatal treatment with zidovudine. We also analyzed data on the timing of zidovudine prophylaxis collected by chart review in a subgroup of 454 infants as a means of validating the results in the entire cohort.

Results: From August 1, 1995, through January 31, 1997, specimens from 939 HIV-exposed infants who were 180 days of age or younger were submitted for PCR testing. The rates of perinatal HIV transmission varied depending on when zidovudine prophylaxis was begun. When treatment was begun in the prenatal period, the rate of HIV transmission was 6.1 percent (95 percent confidence interval, 4.1 to 8.9 percent); when begun intra partum, the rate was 10.0 percent (3.3 to 21.8 percent); when begun within the first 48 hours of life, the rate was 9.3 percent (4.1 to 17.5 percent); and when begun on day 3 of life or later, the rate was 18.4 percent (7.7 to 34.3 percent). In the absence of zidovudine prophylaxis, the rate of HIV transmission was 26.6 percent (21.1 to 32.7 percent).

Conclusions: These results confirm the efficacy of zidovudine prophylaxis and suggest that there are reductions in the rates of perinatal transmission of HIV even with the use of abbreviated regimens that are begun intra partum or in the first 48 hours of life.