Results of a prenatal screening program for the human immunodeficiency virus in a cross-sectional population.

A prenatal screening program for antibody to the human immunodeficiency virus (HIV) was examined prospectively in a cross-sectional population. Routine screening was performed on 3,241 women during the first trimester. Serum samples yielding repeatedly positive results on an enzyme-linked immunosorbent assay (ELISA) (n = 6) were subjected to confirmatory Western blot testing. All the specimens were determined to be false positive with atypical banding regions not consistent with HIV-1 infection. This false-positive rate was higher than in previous reports of screening programs in low-risk populations (P less than .005). Since antibody to HIV may not be detectable for several months after infection, we serially tested 984 of the women in different trimesters of pregnancy to determine whether repeat testing would yield seroconversion undetected at the first screening. No patient who initially tested negative on the ELISA tested positive later in gestation. We therefore recommend that routine screening be performed only once during pregnancy, preferably in the first or early second trimester, in the general population.