ObjectiveTo identify risk factors associated with low postpartum hematocrits after vaginal delivery and to define lower risk categories of patients for whom routine determination of hematocrit may not be necessary.MethodsThis case-control study was designed to identify risk factors for discharge hematocrit below 27% in nonanemic patients after a vaginal delivery using the University of California, San Francisco, Perinatal Database. Multivariate statistics were used to determine the most significant risk factors. Lower risk subpopulations were analyzed to determine their rate of low discharge hematocrits.ResultsRisk factors associated with odds ratios greater than 1.5 for discharge hematocrit less than 27% included estimated blood loss greater than 500 mL, placenta previa, abruption, prolonged third stage, preeclampsia, prior post-partum hemorrhage, and prior cesarean delivery. Estimated blood loss > 500 mL was the most significant risk factor for discharge hematocrit less than 27% (odds ratio 4.5, 95% confidence interval 3.8, 5.4). A population without statistically significant risk factors was identified; this group had a 1.4% risk of discharge hematocrit less than 27%.ConclusionRoutine postpartum hematocrits are unnecessary in clinically stable patients with an estimated blood loss of less than 500 mL.