Mild Thrombocytopenia and Postpartum Hemorrhage in Nulliparous Women With Term, Singleton, Vertex Deliveries

To assess whether mild thrombocytopenia (platelet count 100-149 k/microliter) is associated with an increased risk of postpartum hemorrhage.

Nulliparous women with term, singleton, vertex pregnancies undergoing labor at our institution between August 2016 and September 2017 were included. The primary exposure was mild thrombocytopenia, defined as platelet count 100-149 k/microliter, and the comparator was normal platelet count (150 k/microliter or greater). Those with severe thrombocytopenia (platelet count less than 100 k/microliter) were excluded from analysis. The primary outcome was postpartum hemorrhage, determined by International Classification of Diseases, Tenth Revision codes and the hospital discharge problem list. Secondary outcomes included use of uterotonic agents (methylergonovine maleate or carboprost tromethamine), total blood loss 1,000 mL or greater, and blood transfusion. Data were analyzed by t test, χ or Fisher exact test, and multivariable logistic regression, with significance at α <0.05.

We evaluated 2,845 eligible women, of whom 2,579 (90.2%) had normal platelet count 150 k/microliter or greater, 266 (9.3%) had platelet count 100-149 k/microliter (mild thrombocytopenia), and 13 (0.5%) had platelet count less than 100 k/microliter (severe thrombocytopenia). Compared with women with normal platelet count, those with mild thrombocytopenia had a higher rate of postpartum hemorrhage (16.9% vs 8.5%, P<.001) and were more likely to have total blood loss 1,000 mL or greater (4.5% vs 1.7%, P=.002) and receive methylergonovine maleate (10.5% vs 5.9%, P=.003) or carboprost tromethamine (6.0% vs 1.6%, P<.001) or both (3.8% vs 1.0%, P<.001), but rates of blood transfusion were no different (1.9% vs 1.5%, P=.59). The association between mild thrombocytopenia and postpartum hemorrhage persisted after multivariable adjustment for potential confounders (adjusted odds ratio 2.2, 95% CI 1.5-3.2, P<.001).

Among nulliparous women with term, singleton, vertex pregnancies undergoing labor, those with mild thrombocytopenia (platelet count 100-149 k/microliter) had a twofold greater likelihood of postpartum hemorrhage compared with those with normal platelet count.