Declining mother-to-child HIV transmission following perinatal zidovudine recommendations, United States

Objective: To evaluate the risk and risk factors for mother-to-child HIV transmission since recommendations for using zidovudine (ZDV) to prevent mother-to-child transmission were published in August 1994. Methods: Since 1986. the CDC Perinatal AIDS Collaborative Transmission Study (PACTS) has enrolled HIV-infected pregnant women and their children in a prospective study of mother-to-child HIV transmission. We analyzed data on prenatal and newborn ZDV use. maternal CD4+ lymphocyte count within 90 days of delivery, maternal clinical status, date of delivery, duration of ruptured membranes, and child infection outcome. Children who tested positive twice by virologie tests (HIV co-culture, DNA-PCR, p24 antigen) or by HV antibody after 15 months of age or had AIDS were considered infected: children without AIDS who tested negative twice by virologie tests (≥1 after 2 months of age) or by HIV antibody test were considered uninfected. Results: Of 1183 mother-child pairs with child infection outcomes. 235 (20%) were infected Of 1019 children bom before 9/1/94.217 (21%) were infected.compared with 18 (I IX) of 164 bom afterwards (RR= 1.9.95%CI= 1.2-3.0). Rsk for transmission was tower with prenatal and/or neonatal ZDV use (RR=0.7.95%CI = 05-0.9), and higher with delivery following rupture of membranes (ROM) for ≥4 hours (RR=1.7,95%CI = l3-12), maternal CD4+ lymphocyte count <500 cells/μl (RR=2.0, 95%CI= 1.4-28), or maternal Class C HIV disease (RR= 1.7.95%CI= 1.1-17).The prevalence of prenatal and/or neonatal ZDV use increased from 11% among women who delivered before 9/1/94 to 8056 among those delivering afterwards (p<0.001). The proportion of deliveries occurring ≥4 hours after ROM decreased during this period (55% vs 37%. p<0.001 ). whereas the proportions of women with CD4+ lymphocyte counts <500 cells/μl and with Class C disease did not change significantly. Conclusions: The mother-to-child transmission risk has declined among PACTS enrollees following publication of the ZDV recommendations. Lower transmission risk may be due not only to increasing ZDV use, but also to decreasing prevalence of other risk factors, such as long duration of ROM.