Delayed villous maturation (DVM) is a spectrum of placental disease characterized by decreased tertiary villus formation, reduced vasculosyncytial membrane formation, and, in its more severe forms, increased large bullous villi. In some series it has been associated with an increased risk of stillbirth in the late third trimester, but overall there are few data on its significance. The aim of this study was to assess perinatal factors associated with, and the clinical significance of, the finding of DVM on placental histology. This was a retrospective study investigating all pregnancies with DVM diagnosed on placental histology in a tertiary level unit between December 2001 and August 2006. Over a 6-year period, 2915 placentas were triaged for histopathological assessment, representing 6.1% of all 48 054 deliveries in this time period. One hundred ninety (6.3%) of these selected cases showed DVM. Fifteen placentas from infants with less than 34 completed weeks of gestation were excluded, leaving 175 for further analysis. When compared with controls matched for gestation and delivering within the same time period (n = 175), DVM was significantly associated with pregestational diabetes (8% vs 2.8%, P < .05; relative risk 2.8 [95% confidence interval 1.03-7.6]), gestational diabetes (8.6% vs 3.4%, P < 0.05; relative risk 2.5 [95% confidence interval 0.99-6.3]), and prenatal or intrapartum intrauterine death (8.6% vs 0%, P < 0.05). Delayed villous maturation is associated with both gestational and pregestational diabetes mellitus and with perinatal death.