1472 Risk Factors for Mother - to - Infant Transmission of Hiv - 1 Infection in 66 Sets of Twins * by Birth Order

ADDRESSES Viral Epidemiology Section(J. J Goedert, MD, R. J. Biggar, MD) and Family Studies Section (C. I. Amos, PhD), National Cancer Institute, Rockville, Maryland; Division of Clinical Research, Genentech Inc, South San Francisco, California (A-M. Duliège, MD); and Research Triangle Institute, Washington, DC, USA (S. Felton, MA). Correspondence to Dr James J. Goedert, 6130 Executive Blvd, Suite 434, Rockville, Maryland 20852, USA. To examine the epidemiology and natural history of mother-to-infant transmission of human immunodeficiency virus type 1 (HIV-1), especially genetic and intrapartum exposure factors, we obtained data on twins and triplets born to women infected with the virus. 40 investigators in nine countries contributed demographic, clinical, and epidemiological data on 100 sets of twins and 1 set of triplets. Among the 66 evaluable sets, HIV-1 infection was more common