Proposed Definitions for in Utero versus Intrapartum Transmission of HIV-1

Abstract
An important issue in understanding and preventing the vertical transmission of human immunodeficiency virus type 1 (HIV-1) from a woman to her child is the timing of such transmission. Cases of in utero1 , 2 and postpartum (through breast-feeding3) transmission have both been documented. Recent evidence suggests that vertical transmission can occur during the intrapartum period and that it may be a major mode of infection.4 5 6 7 In the United States, in utero and intrapartum transmission account for the majority of HIV-1 infections in infants.