Subjects and Methods

WITS. The present analysis was conducted using retrospective data obtained from mother‐infant pairs enrolled in the WITS cohort during 1989–2004. WITS is a prospective observational, multicenter study that was established in 1989. The study population is recruited from 6 sites in the United States and Puerto Rico (Boston and Worcester, Massachusetts; Brooklyn and Manhattan, New York; Chicago, Illinois; Houston, Texas; and San Juan, Puerto Rico). HIV‐infected women were recruited during pregnancy and monitored at regular intervals throughout pregnancy, delivery, and the postpartum period. Data obtained from mothers include the use of ARV drugs before and during pregnancy, hard drug use, and maternal medical complications. Their children are monitored at regular intervals from birth, and clinical and laboratory parameters are recorded at regular intervals. Flow‐cytometric analysis was performed and controlled for quality as described elsewhere. Informed consent was obtained from all women before their participation in the study. All research activities were approved by institutional review boards at each local site, in accordance with federal guidelines and regulations for the conduct of research involving human subjects.
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Study population. Data from singleton pregnancies resulting in HIV‐exposed but uninfected infants were analyzed. An infant was defined as HIV‐uninfected if 2 HIV virologic tests were negative at or after age 1 month and at or after age 4 months or if 1 HIV serologic test was negative after age 18 months. Perinatal maternal and infant ARV use was categorized as “no ARV” (no ARV use during pregnancy or by the infant after birth), and “any ARV” (ARV use during pregnancy and/or by the infant). The any‐ARV group consisted of 2 large groups: ARV monotherapy (1 antiretroviral drug used during pregnancy and/or by the infant) and ARV combination therapy (2 ARVs or highly active ARV therapy used during pregnancy and/or by the infant). The ARV combination therapy group was further divided into 2 subgroups: persons who received protease inhibitors (PIs) and persons who did not. In general, as in previous WITS analyses, mother‐infant pairs in the no‐ARV group were from before 1994, those in the ARV monotherapy group were from 1994 to 1997, and those in the ARV combination therapy group were from subsequent years.

Hard drug use during pregnancy was defined as the use of cocaine, heroin/opiates, methadone, and/or injection drugs as ascertained by self‐report and/or positive urine toxicologic results at prenatal or delivery visits. Infants were evaluated and blood was collected at age 0–7 days (usually within the first 48 h of life), at ages 6–10 days and 1 and 2 months, and at 2–6‐month intervals thereafter. For most analyses, laboratory data were divided into 2 groups: data from blood collected during the first 2 months of life (0–7 days and 2 months) and data from blood collected from age 6–24 months (6, 12, 18, and 24 months). Infants who had laboratory values for at least 1 study visit were included in the analysis. The variables evaluated included hemoglobin concentration and platelet, neutrophil, total lymphocyte, and CD4+ and CD8+ cell counts.