High- but not low-grade histologic chorioamnionitis is associated with spontaneous preterm birth in a Swedish cohort.

Objective: To examine whether different grades of placenta inflammation are associated with risk for spontaneous preterm birth, taking into consideration maternal and delivery factors. Placentas from spontaneous preterm births were compared with a control group from full-term deliveries.

Methods: Placentas from 98 full-term, 71 late preterm (gestational week 34-37), and 65 early preterm (gestational week 22-33) singleton deliveries were analysed from the Karolinska University Hospital in Stockholm.