[Singleton placentas with abnormal shape: a clinicopathological analysis of 130 cases].

To investigate the pathological characteristics of singleton placenta with abnormal shape and its influence on the outcome of maternal-fetal pregnancy. The clinicopathological data of singleton placentas with abnormal shape from January 2014 to December 2020 in the Department of Pathology, Haidian Maternal and Children Health Hospital were analyzed retrospectively. There were 130 singleton placentas with abnormal shape in this cohort, including 48 succenturiate placentas, 12 bilobed placentas, 50 marginate placentas, 13 circumvallate placentas, 3 annular placentas, 2 membranous placentas and 2 fenestrated placentas. Gestational age ranged from 29 to 40 weeks. There were 51 cases of premature rupture of membranes, 11 cases of placenta previa, 5 cases of placental abruption, 15 cases of placental adhesion/implantation and 27 cases of postpartum hemorrhage. There were 46 preterm fetuses,28 fetuses with fetal growth restriction, 22 fetuses with intrauterine distress, and 1 fetus with intrauterine death. Grossly, the placental lobules of succenturiate placentas had apparent size difference, while two lobules of bilobate placenta were more consistent. The chorionic plate size was smaller than the bottom plate of circumvallate placenta, the folded fetal membrane in the rim of placenta was thickened (termed marginate placenta if there was no thickening). The membranous placenta was characterized by a thin, large membrane-like shape. Annular placenta showed characteristic hollow cylinder, ring or horseshoe-shape. Fenestrated placenta was characterized by tissue defects near central area. Microscopically, functional/morphologic changes were the main manifestations of inadequate maternal-fetal perfusion, including villous infarction, distal villous dysplasia and excessive villous maturation. The abnormal shaped singleton placentas showed variable extent of inadequate maternal-fetal perfusion, which may lead to adverse pregnancy outcomes such as premature delivery, fetal growth restriction, intrauterine distress or fetal death.