Neonatal outcomes following preterm birth classified according to placental features

Preterm birth has staggering health implications, and yet the causes of most cases are still unknown. Placental features have been understudied as an etiology for preterm birth, and the association between placental pathologic lesions and neonatal outcomes are incompletely understood.

We sought to characterize births according to placental pathology and relate these to adverse neonatal outcomes.

We studied 20,091 births (15,710 term and 4381 preterm) with placental evaluations. Births were classified according to the presence or absence of placental lesions consistent with malperfusion (vasculopathy, infarct, advanced villous maturation, perivillous fibrin, fibrin deposition) and intrauterine inflammation/infection (chorioamnionitis, funisitis, vasculitis). Outcomes were gestational week of delivery, birthweight z-score, neonatal respiratory distress syndrome, and intraventricular hemorrhage.

Among all preterm births, evidence of placental malperfusion was identified more often than inflammation/infection (50.6% vs 27.3%, P < .0001). Placental malperfusion was associated with reduced fetal growth (adjusted birthweight z-score, -0.83, P < .0001) and lesions of inflammation/infection were associated with earlier delivery (adjusted difference -2.08 weeks, P < .0001) than those with no lesions. When both placental lesions were present, earlier delivery (adjusted difference -2.28 weeks, P < .0001) and reduced fetal growth (adjusted birthweight z-score difference, -0.24, P = .001) were observed more often than when neither lesion was present. Findings were similar when restricted to cases of spontaneous preterm birth. Intraventricular hemorrhage was higher in preterm births with malperfusion lesions than cases with no lesions (7.6% vs 3.4%; odds ratio, 1.98; confidence interval, 1.18-3.32), accounting for gestational age and other covariates.

Placental pathology provides important insight into subtypes of preterm birth with adverse neonatal outcomes. Co-occurrence of malperfusion and inflammation/infection, especially among spontaneous preterm births, may be a novel pattern of placental injury linked to severe adverse outcomes.