Placental biomarkers in second trimester maternal serum are associated with postpartum hemorrhage: a secondary analysis of the NuMoM2b dataset

Postpartum hemorrhage (PPH) is the leading cause of maternal mortality worldwide, which is often attributed to retained placenta (RP) after delivery. There are no biomarkers currently used to predict a risk of developing RP/PPH prior to labor. The objective of this study was to determine relationships between placental biomarkers measured in the first and second trimesters and proxy measures of postpartum blood loss relative to preeclampsia status in the Nulliparous Pregnancy Outcomes Study: Monitoring Mothers-to-Be (nuMoM2b) dataset. 2,192 participants had placental analytes drawn during the first and second trimesters (9-13 and 16-22 weeks gestation, respectively); the outcome was a composite of retained placenta and/or PPH requiring blood transfusion (RP/PPH). Using Kruskal-Wallis tests, median differences in levels of soluble fms-like tyrosine kinase-1 (sFlt-1), placental growth factor (PlGF), sFlt-1/PlGF ratio, soluble endoglin (sEng), beta subunit of human chorionic gonadotropin ({beta}-hCG), inhibin A (INHA), and pregnancy-associated protein-A (PAPP-A) were assessed between women with (n=67) and without (n=2125) RP/PPH overall and stratified by preeclampsia status. Women with RP/PPH had significantly higher median levels of sEng, {beta}-hCG, INHA, PAPP-A in the second trimester and sFlt-1was higher in both first and second trimesters, which was observed again when stratifying by preeclampsia status. Our findings indicate that biomarkers associated with angiogenesis, particularly when measured in the second trimester, are important targets for further study of RP and/or PPH pathophysiology and potential risk screening development.