Background: Postpartum hemorrhage (PPH) is the leading cause of maternal mortality. To evaluate the possibility that antepartum fibrinogen is associated with risk of postpartum hemorrhage. Methods and Findings: Retrospective analysis was performed among 949 women with vaginal deliveries of singletons at gestational week (GW) ≥ 36 to examine associations of PPH, defined as estimated blood loss (EBL) ≥ 700 mL, with antepartum blood fibrinogen, platelet count, and hemoglobin levels within 7 days prior to delivery and demographic characteristics, including, parity, maternal age, pre-pregnancy body mass index, duration of labor, instrumental delivery, and birthweight. Logistic multiple regression analysis was performed to identify independent risk factors and odds ratios (OR). PPH occurred in 127 (13%) women and was less frequent as levels of fibrinogen increased with OR (confidence interval) 0.97 (0.95 – 0.99) for 1.0 g/L increase in fibrinogen level by logistic multiple regression analysis. The other independent risk factors for PPH included nulliparity,1.08 (1.03 – 1.12) and increased birthweight 1.02 (1.01 – 1.03) for each 100 g increase in birthweight. PPH was more common in nulliparous than multiparous women (16% [77/474] vs. 11% [50/475]) and in women with instrumental deliveries (27% [8/30] vs. 13% [119/919]). EBL was significantly negatively correlated with fibrinogen and hemoglobin levels and positively with GW at delivery and infant birthweight. Antepartum fibrinogen level was an independent risk factor for PPH, and each 1.0 g/L decrease of antenatal fibrinogen level increased the risk of PPH by 2.9% independent of other factors. 

Fibrinogen, a positive acute-phase protein elevating in any form of inflammation as well as in pregnancy, is the soluble precursor of fibrin and a key contributor to both primary and secondary hemostasis, promoting clot formation and platelet aggregation. Patients with hypofibrinogenemia (defined as a fibrinogen level<1.5 g/L) are prone to bleeding when exposed to trauma or after giving birth. Although fibrinogen levels differ considerably between assay methods, blood fibrinogen level increases to approximately double during pregnancy suggesting a physiological role of increased fibrinogen level in maintaining pregnancy and postpartum hemostasis.

Postpartum hemorrhage (PPH) is the leading cause of maternal mortality and is associated with 12.5% – 19.1% of maternal mortalities in the USA. PPH accounted for 14.1%, 9.7%, and 6.7% of all causes of maternal mortality in Japan in 2000, 2005, and 2010, respectively. Various etiologies, such as uterine rupture, uterine inversion, retained placenta, and severe birth canal injury, may be identified in some cases of PPH, but the definite etiology remains unclear in the majority of cases. Although the leading etiology of PPH is uterine atony, this is poorly defined at present and represents a diagnosis of exclusion. Twin pregnancy is a risk factor of PPH Uterine overdistension is considered to be attributable to PPH via uterine atony in twin pregnancy. However, fibrinogen level determined at the initial stage of PPH is known to be a good predictor of subsequent severe PPH and women with twin pregnancy are likely to exhibit a gradual decline in fibrinogen level in the last several weeks of pregnancy leading to lower antepartum fibrinogen level compared to those with singleton pregnancies . These observations suggest that a low antepartum fibrinogen level may be associated with higher risk of PPH. Indeed, at least two studies suggested that lower antepartum fibrinogen level was associated with increased risk of PPH. However, many demographic characteristics other than antepartum fibrinogen levels may influence the risk of PPH. This retrospective study was conducted to determine independent risk factors for PPH.

With Regards,
Sara Giselle
Associate Managing Director
Journal of Critical Care Obsestrics & Gynocology