HIV levels in mother's blood predicts risk of perinatal transmission

Abstract

The concentration of HIV in a pregnant woman's blood gives the best indication of the risk that the virus will be passed to her infant, according to two new US studies. The first study came from data collected as part of the Pediatric AIDS Clinical Trials Group Study 185, which was designed to compare the effectiveness of zidovudine alone with zidovudine plus passive immunotherapy in preventing perinatal HIV trans mission. Lynne Mofenson of the US Centers for Disease Control and Prevention (Atlanta, GA) led the study. In addition to maternal HIV-1 RNA levels, Mofenson and her co-workers looked to see whether perinatal HIV transmission could be linked to such risk factors as low CD4+ lymphocyte counts, low HIV-1 p24 antibodies, and chorioamnionitis at time of delivery. But the only independent risk factor proved to be maternal HIV-1 RNA concentrations measured at baseline (upon entry into the trial), which were associated with 2·4 increased risk per log increase in the number of copies (95%CI 1.2–4.7, p= 0.02), and concentrations at time of delivery, which were associated with an 3.4 increased risk (95%CI 1.7–6.8, p=0.001). “There was no transmission of HIV-1 among the 84 women who had levels of HIV-1 below the limit of detection (500 copies per milliliter) at base line or the 107 women who had undetectable levels at delivery”, the researchers report (N Engl J Med 1999; 341: 385–93). The second paper came from the Women and Infants Transmission Study, an ongoing study of perinatal HIV transmission. Patricia Garcia from Northwestern University (Chicago, IL) co-workers also found that viral load alone was a strong indicator of the risk of transmission (N Engl J Med 1999; 341: 394–402). The rate of transmission was 0% among women with plasma viral RNA amounts lower than 1000 copies/ mL; 16.6% among those with 1000–10 000 copies/ mL; 21.3% among those with 10 001–50 000 copies/mL, 30.9% with levels of 50 001–100,000 copies/ mL, and 40.6% with more than 100 000 copies/mL