Since maternal sexually transmitted diseases or chorioamnionitis may increase the risk of vertical HIV transmission, efforts to prevent, detect, or treat these infections are important. Similarly, since active drug use may increase the risk of perinatal transmission (Landesman et al., 1996; Rodriguez et al., 1996) and may interfere with the ability of expectant women to seek and comply with appropriate medical care, efforts to improve access to drug treatment programs for pregnant women are also important.

As previously discussed, a majority of infants acquire HIV infection during delivery through mucosal exposure to maternal blood and/or vaginal secretions. Optimizing obstetrical practices (e.g., limiting the duration of rupture of membranes prior to delivery, avoidance of invasive procedures including scalp electrodes during delivery) might help to limit the risk of transmission. Cesarean section has been proposed as a means of reducing the risk of exposure, particularly if performed prior to the rupture of membranes. A meta-analysis suggested that cesarean section might protect against vertical HIV transmission (Rogers, 1997). In a recently reported study, cesarean section appeared to reduce the risk of vertical HIV-1 transmission; however, the benefit of cesarean section was only apparent when performed prior to the onset of labor and in mother-infant pairs who received ZDV (Mandelbrot et al., 1998). Virocidal cleansing of the birth canal prior to vaginal delivery has also been proposed as a means of reducing intrapartum HIV transmission, though a study in Malawi that evaluated chlorhexidine vaginal cleansing during labor did not find an overall reduction in transmission (Biggar et al., 1996). There was, however, a reduction in transmission if the chlorhexidine was administered to women whose membranes ruptured at least four hours prior to delivery (Biggar et al., 1996).

Diagnosis Of HIV Infection In Women And Infants

The HIV testing algorithm recommended by the Public Health Service (PHS) for pregnant women is comprised of initial screening with a Food and Drug Administration (FDA) licensed enzyme-linked immunosorbent assay (ELISA). Confirmatory testing of repeatedly reactive ELISAs with an FDA-licensed supplemental test (e.g., Western blot or immunofluorescence assay) must be done. The diagnosis of HIV infection in adults requires that both the ELISA and the confirmatory test be positive. According to the manufacturers, the third generation ELISAs are 100% sensitive (probability that the test will be positive if the individual tested is truly infected) in individuals infected long enough to have developed HIV antibodies and 99.9% specific (probability that the test will be negative if the individual tested is truly not infected). Despite these excellent performance characteristics, there may be a problem with false positive results in low-prevalence areas. For example, in a population of pregnant women where the prevalence of HIV is 0.03%, only 23% of samples with positive ELISA would be found to be truly positive by confirmatory Western blot test. In a high-prevalence



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