Association of acute histological chorioamnionitis and other placental lesions with subsequent pregnancy outcomes after spontaneous preterm birth.

Objective: Acute histological chorioamnionitis (HCA) is detected in over 50% of spontaneous preterm birth (PTB) and is associated with worse neonatal prognosis. We aim to investigate whether the presence of HCA impacts subsequent pregnancy outcomes.

Methods: This retrospective cohort study included deliveries at a tertiary center from 2014 to 2020. Participants were individuals with a history of spontaneous PTB or pregnancy loss >16 weeks and available placental pathology (index pregnancy) with a subsequent pregnancy followed at the same institution. Placentas were classified according to the presence of HCA, other placental lesions, or no lesions. Subsequent pregnancy outcomes were analyzed. Primary outcome was the rate of overall and spontaneous PTB (<37 weeks ) in the subsequent pregnancy.

Results: A total 292 individuals met study criteria, of which 133 had HCA, 61 had other placental lesions, and 98 had no lesions. Individuals with HCA in the index delivery had higher risk of PTB <28 weeks in the subsequent pregnancy, compared to the no-lesion group (10.4% vs 1.0%, P = 0.004). Rates of PTB >28 weeks did not significantly differ. The risk of neonatal adverse composite outcomes was higher in the HCA group (13.9% vs 4.2%, P < 0.01). In a sub-analysis of different placental lesions at the index PTB, only maternal vascular malperfusion was associated with recurrent PTB (aOR 2.57, P = 0.01).

Conclusion: PTB with HCA is associated with higher rates of extreme PTB and adverse neonatal outcomes in the subsequent pregnancy. The inclusion of placental pathology analysis may improve individualized risk assessment in future pregnancies.