OBJECTIVETo evaluate the contribution of placental histopathology to the diagnosis of congenital syphilis.METHODSFrom January 1, 1986, through December 31, 1998, all pregnant women presenting to a large, urban Dallas County labor and delivery unit with untreated syphilis at delivery and who had placental evaluation performed were identified. Women were clinically staged, and the infants were evaluated for congenital syphilis using a standard protocol. Each placenta was evaluated by two independent pathologists. Histologic characteristics of the placenta related to congenital syphilis in live-born and stillborn infants were then analyzed.RESULTSSixty-seven women met the study criteria: 33 (49%) stillborn and 18 (27%) live-born infants with congenital syphilis, 15 (22%) uninfected live-born infants, and one uninfected stillborn fetus diagnosed by current criteria. There were no differences between the groups with regard to demographic characteristics, prenatal care, or stage of syphilis. Stillborn infants were more likely to deliver pre-term (P< .001). Controlling for gestational age, histopathology revealed necrotizing funisitis, villous enlargement, and acute villitis associated with congenital syphilis. Erythroblastosis was more common in stillborn infants with congenital syphilis than all live-born infants (odds ratio 16, 95% confidence interval 1, 370). The addition of histologic evaluation to conventional diagnostic evaluations improved the detection rate for congenital syphilis from 67% to 89% in live-born infants, and 91% to 97% in stillborn infants.CONCLUSIONOur results show that histopathologic examination of the placenta is a valuable adjunct to the contemporary diagnostic criteria used to diagnose congenital syphilis.