Impact of anemia and thrombocytopenia on postpartum hemorrhage risk among women with term singleton pregnancy

Both thrombocytopenia (platelet count < 150 × 10³/µL) and anemia have been associated with postpartum hemorrhage (PPH). However, the impact of thrombocytopenia on PPH risk among women with mild and severe anemia is unknown. We sought to evaluate the association between thrombocytopenia and anemia in increasing risk of PPH. We performed a secondary analysis of a retrospective cohort of pregnant women from 19 hospitals across the United States from 2016 to 2021. Women who had a term singleton pregnancy and hematocrit (Hct) ≤ 33% at delivery were included in the study. The primary outcome was PPH (defined as blood loss ≥ 1000 mL or blood transfusion). We also analyzed the effect of severe anemia (Hct < 28%) on the association between PPH and thrombocytopenia. Chi-squared tests and Fisher’s exact tests were used for categorical variables and an independent t-test was used for continuous variables. There were 20,808 women who met our inclusion criteria, of which 1793 (8.6%) had platelet count < 150 × 10³/µL. The prevalence of PPH was 6.4%. Compared with women with normal platelet count, those with thrombocytopenia had 1.3-fold higher odds of PPH [6.8% vs. 4.5%, adjusted OR 1.3 (1.1–1.7)]. Platelet count ≥ 150 × 10³/µL was associated with decreased odds of PPH among patients with hct between 28 and 33% and hct < 28%. In conclusion, anemic women with term singleton pregnancies who delivered with thrombocytopenia had a higher frequency of PPH. Normal platelet count at delivery was protective against PPH in the setting of anemia regardless of severity.