Placental Vascular Pathology Findings and Pathways to Preterm Delivery

There is limited data on the role of specific maternal placental vascular findings in influencing preterm delivery. This prospective population-based cohort study examined possible associations between placental vascular pathology and preterm delivery in a subcohort of pregnant women enrolled in the Pregnancy Outcomes and Community Health Study. The study was conducted between 1998 and 2004 in 5 Michigan communities. A total of 1053 placentas (239 preterm, 814 term) from pregnancies ending in both spontaneous and medically indicated preterm delivery <37 weeks' gestation and from women who delivered at term were analyzed. Histologic evaluation identified 29 placental vascular variables which were grouped into 5 pathology-based groups. Of the 5 groups, 3 were maternal lesions: vascular–obstructive lesions (MV-O); vascular–disturbance of integrity (MV-I); and vascular–developmental (characterized by abnormal or incomplete remodeling of maternal spiral arteries (MV-D). The remaining 2 groups were fetal lesions: vascular–obstructive (FV-O) and vascular–disturbance of integrity (FV-I). Within each group, pathology-based vascular continuous construct scores were obtained by adding the number of positive findings and calculating a dichotomous variable to approximate the top quintile, scored as “0” (high), and the bottom 4 quintiles, scored as “1” (not high). Polytomous logistic regression models were used to adjust for potential confounders. High scores for each of the five groups were associated with medically indicated preterm delivery at <35 weeks, with unadjusted odds ratios ranging from 2.9 to 6.5. After adjustment for confounders, the association remained statistically significant. There was a significant association between the risk of spontaneous preterm delivery at 35 to 36 weeks and a high score for any one of 3 groups: MV-I, MV-D, and FV-I, with adjusted odds ratios ranging from 2.2 to 4.6. A significant association was found between the risk of spontaneous preterm delivery at <35 weeks and the presence of 2 or more high scores for 3 groups: MV-I, MV-D, and FV-I, with adjusted odds ratios ranging from 4.1 to 7.4. Neither MV-O nor FV-O was related to spontaneous preterm delivery. These findings show that a model based on a grouping of pathology-based vascular placental lesions offers insights into pathways for medically indicated and spontaneous preterm delivery and support the evaluation in future studies of individual placenta vascular findings within each construct.