Risk of recurrent preterm birth and placental pathology

OBJECTIVE: To estimate whether placental pathological lesions from an index preterm birth are associated with an increased risk of recurrent preterm birth and to estimate whether certain pathologic lesions recur in a woman's next delivery. METHODS: We performed a retrospective cohort study of all women who delivered at less than 37 weeks and had their next delivery at our institution during a 5-year period. Women were included in the cohort if placental pathology was available from their preterm birth. Placental pathology from their subsequent birth was also collected. Placental pathology was classified into presence or absence of two classes of lesions-inflammatory and thrombotic. Variables considered as possible confounders included race, gestational age of preterm birth, interpregnancy interval, tobacco use, payor status, years of education, and maternal medical problems. RESULTS: Inflammatory lesions (n=173) were associated with recurrent preterm birth overall as well as recurrent spontaneous preterm birth (P <.001). Thrombotic lesions (n=158) were not associated with recurrent preterm birth or any subtypes of preterm birth. The association between inflammatory lesions and recurrent spontaneous preterm birth remained significant when controlling for gestational age of preterm birth, race, and tobacco use, with an adjusted odds ratio of 2.4 (95% confidence interval 1.2-4.7). Inflammatory placental lesions (n=194) were associated with inflammatory lesions in the subsequent delivery P=.001). CONCLUSION: Recurrent preterm birth is more likely among women with inflammatory lesions on placental pathology from a prior preterm birth. Additionally, these women are more likely to have placental inflammatory lesions with their next delivery.