Placental characteristics and risks of maternal mortality 50 years after delivery

Introduction: Adverse pregnancy outcomes such as preterm delivery and preeclampsia are associated with a higher maternal risk for subsequent cardiovascular disease (CVD) and all-cause mortality. While such pregnancy conditions are related to abnormal placentation, little research has investigated whether pathologic placental measures could serve as a risk factor for future CVD mortality in mothers.

Methods: Longitudinal study of 33,336 women from the Collaborative Perinatal Project (CPP; 1959-1966) linked to mortality information through December 2016. Pathologists took extensive morphological and histopathological measures. Apart from assessing associations with morphological features, we derived an overall composite score and specific inflammation-related, hemorrhage-related, and hypoxia-related pathologic placenta index scores. Cox regression estimated hazard ratios (HR) and 95% confidence intervals (CI) for mortality adjusting for covariates.

Results: Thirty-nine percent of women died with mean (standard deviation, SD) time to death of 39 (12) years. Mean (SD) placental weight and birthweight were 436 g (98) and 3156 g (566), respectively. Placenta-to-birthweight ratio was associated with all-cause mortality (adjusted HR 1.03: 1.01, 1.05 per SD in ratio). In cause-specific analyses, it was significantly associated with respiratory (HR 1.06), dementia (HR: 1.10) and liver (HR 1.04) related deaths. CVD, cancer, diabetes and kidney related deaths also tended to increase, whereas infection related deaths did not (HR 0.94; 0.83, 1.06). Placental measures of thickness, diameters, and histopathological measures grouped by inflammatory, hemorrhagic, or hypoxic etiology were not associated with mortality.

Discussion: Placental weight in relation to birthweight was associated with long-term maternal mortality but other histopathologic or morphologic features were not.