Optimal predelivery hemoglobin to reduce transfusion and adverse perinatal outcomes

Maternal anemia has been associated with poor obstetrical outcomes; however, the optimal hemoglobin level for reducing blood transfusion at delivery has not been well-defined.

This study aimed to measure the association of maternal anemia immediately before delivery with peripartum transfusion and other adverse perinatal outcomes. We also sought to identify the optimal hemoglobin level for predicting transfusion.

This was a retrospective cohort study of patients who had hemoglobin or hematocrit collected before delivery of live, nonanomalous neonates at ≥23 weeks' gestation at a single center (2013-2018). Patients were excluded if they had sickle cell disease or were receiving anticoagulation. Patients were categorized as having anemia or no anemia on the basis of predelivery hemoglobin or hematocrit levels using criteria set by the American College of Obstetricians and Gynecologists. The primary outcome was transfusion of ≥1 unit of packed red blood cells during the delivery admission. Secondary outcomes included select adverse perinatal outcomes. Bivariable analyses compared baseline characteristics and outcomes between the anemia and no-anemia groups. Multivariable logistic regression estimated the association between anemia and outcomes. The hemoglobin cutoff optimizing sensitivity and specificity for transfusion was identified by the Liu method.

Of the 18,357 patients included in the analysis, 5444 (30%) had predelivery anemia (mean hemoglobin, 10.0±0.8 g/dL) vs 12,913 (70%) who did not (mean hemoglobin, 12.3±1.1 g/dL). Patients with anemia were more likely to be non-Hispanic Black and publicly insured and less likely to be nulliparous. Anemia was associated with 5-fold higher odds of packed red blood cell transfusion (6.0% vs 1.3%; adjusted odds ratio, 5.23 [95% confidence interval, 4.09-6.69]) compared with no anemia. For each 1 g/dL increase in predelivery hemoglobin, the odds of transfusion were 56% lower (adjusted odds ratio, 0.44 [confidence interval, 0.40-0.48]). The optimal hemoglobin for prediction of transfusion was 10.6 g/dL (sensitivity: 80%, specificity: 86%). There was no association between anemia and composite maternal or neonatal morbidity after adjustment for covariates, but anemia was associated with higher odds of postpartum readmission (adjusted odds ratio, 1.35 [1.11-1.64]).

Maternal anemia before delivery was associated with 5-fold higher odds of packed red blood cell transfusion and postpartum readmission, but not other perinatal morbidity. Optimizing predelivery hemoglobin, particularly ≥10.6 g/dL, may reduce peripartum transfusion.