Placental villous hypermaturation is associated with improved neonatal outcomes.

Introduction: Accelerated placental maturation is considered a sign of maternal vascular malperfusion, and is often interpreted as an adaptive, compensatory response by the placenta. We tested this interpretation by comparing outcomes in pregnancies with and without accelerated maturation.

Methods: Using data from the National Collaborative Perinatal Project, we categorized preterm placentas (24-34 weeks, inclusive; 2525 births) by whether they showed placental villous hypermaturation (PVH), i.e., had the appearance of a placenta of 37 weeks or over upon microscopic examination. We assessed whether PVH was associated with maternal race, maternal BMI, fetal sex, type of preterm birth, preeclampsia, signs of infection or inflammation or placental abruption. We also assessed whether placentas showing PVH were associated with improved outcomes in terms of survival, Apgar score, or oxygen use.

Results: PVH was more common in preeclamptic pregnancies and less common in pregnancies complicated by placental abruption or showing signs of placental infection or inflammation. Adjusting for potentially confounding factors, PVH was associated with reduced odds of fetal death, death between birth and 120 days of age, low Apgar scores and oxygen use. PVH was also associated with higher birthweights for gestational age. When correcting for the effect of birthweight, the association between PVH and reduced fetal and neonatal death remained significant.

Discussion: Accelerated placental maturation, as manifested by PVH, is associated with improved outcomes. Our work therefore supports the hypothesis that accelerated maturation is a compensatory response by the placenta to improve its transport capacity in specific pregnancy complications.