The epidemiology of placental features: Associations with gestational age and neonatal outcome

Objective: To investigate the epidemiologic and pathogenetic significance of placental features and neonatal outcome in a high-risk population. Methods: One pathologist examined 1252 placentas from clinically selected at-risk singleton pregnancies. Placental pathology features were analyzed relative to gestational age and status of the newborn, including fetal growth restriction (FGR), low 1-minute Apgar score, infection, liver disorder, anomalies, and death in the immediate postnatal period. Results: The most frequent placental pathologic features were ischemic change, meconium staining, and chorioamnionitis. Only 8% of placentas were considered normal. The number of features per placenta increased with gestational age. Among preterm infants, chorioamnionitis occurred most frequently with low 1-minute Apgar score (40%), clinically apparent infection (43%), liver disorder (43%), and anomalies (42%), compared with healthy newborns (15%). Chorioamnionitis at term was most frequent among infants with low 1-minute Apgar score (26%), infection (30%), and liver disorder (23%), compared with healthy newborns (16%). Meconium and ischemic changes were most frequent in placentas from healthy newborns, compared with affected newborns, regardless of gestational age. Multivariable analyses revealed an independent association between chorioamnionitis and low 1-minute Apgar score (P < .05), and both chorioamnionitis and villitis were associated with newborn infection (P < .05). Conclusion: The frequency of many major pathologic placental features, especially ischemic changes and meconium, in the absence of immediately detectable abnormality is relatively high. Thus, continued follow-up is needed to determine their long-term clinical significance. In addition, associations of ischemic changes and infarction with FGR in term infants suggest the need for comprehensive investigations of the effects of histopathologically apparent low placental blood flow.