Material and Method: Medical records and histology results of the placentas obtained from singleton spontaneous preterm births between 2011 and 2015 at Srinagarind Hospital, Khon Kaen University were reviewed. Preterm births complicated by multiple gestations and medically indicated preterm births were excluded. Accelerated villous maturation was diagnosed by identifying diffuse terminal villi and conspicuous syncytial knotting usually observed in term placentas.

Results: Of 97 spontaneous preterm births, 63 (64.9%) were idiopathic. The associated obstetric complications among the remaining 34 included chorioamnionitis, intrauterine growth restriction, preeclampsia, systemic lupus erythematosus, and maternal heart disease. Accelerated villous maturation was observed in 70 placentas (72.2%). Maternal age and gestational age were significantly associated with accelerated villous maturation. The rate of accelerated villous maturation among idiopathic spontaneous preterm births was comparable with those with other obstetric conditions.

Conclusion: Accelerated villous maturation of placentas among spontaneous preterm births was common. Two significant factors associated with accelerated villous maturation in spontaneous preterm birth were gestational age and maternal age.

Keywords: Accelerated villous maturation, Placental insufficiency, Placental pathology, Preterm birth, Risk factors