The Women and Infants Transmission Study (WITS) of maternal-infant HIV transmission: Study design, methods, and baseline data

Our objective is to describe the Women and Infants Transmission Study (WITS) design, data collection methods, and study cohort characteristics. WITS is a prospective epidemiologic study of the natural history of HIV infection in pregnant women and their infants carried out at obstetric/gynecologic and pediatric clinics in Boston, Chicago, Manhattan, Brooklyn, San Juan, and Houston. The participants were 788 HIV-infected pregnant women and 657 infants born to them. The main outcome measures were clinical and laboratory factors associated with maternal-infant transmission and disease progression in mothers and infants. Eighty-two percent of pregnant women in WITS are women of color. Seventy-two percent of the pregnant women and 81% of infants enrolled as of June 30, 1993, remained in follow-up in March 1994. Among infants followed for at least 6 months from birth and on whom HIV culture results were available, 55 of 310 were infected, with a transmission rate of 17.7%. The WITS has recruited a cohort of HIV-infected pregnant women and their infants who are broadly representative of infected women and infants in the United States. Retention of a cohort of predominantly low-income women, many with chronic substance abuse histories, is challenging but possible. The study is assessing determinants of maternal-infant transmission and disease progression.