Transfusion risk assessment for cesarean delivery: a preoperative tool to guide blood utilization

Cesarean delivery is performed in approximately one-third of pregnancies in the United States and is associated with an increased risk of intrapartum and postpartum hemorrhage. Routine crossmatching of blood for all cesarean deliveries requires substantial resources and may not be necessary for every patient. We aimed to identify preoperative and intrapartum predictors of intraoperative blood transfusion and develop a practical risk stratification tool to support perioperative blood preparation.

We conducted a retrospective cohort study including 3,033 cesarean deliveries performed at a university medical center between 2018 and 2022. Multivariable logistic regression with bootstrap internal validation (10,000 replicates) was used to derive a weighted transfusion risk score. Model performance was assessed by discrimination and calibration across predefined risk groups.

Intraoperative transfusion occurred in 114 cases (3.8%). Independent predictors were placenta previa (aOR 5.14), prior blood transfusion (aOR 4.18), preoperative hemoglobin <11 g/dL (aOR 3.06), suspected intraamniotic infection (aOR 2.43), cervical dilation ≥6 cm (aOR 2.33), uterine fibroids (aOR 2.23), vaginal bleeding (aOR 2.04), and multifetal gestation (aOR 1.83) (all p<0.05). The model demonstrated good discrimination (AUC 0.75). The risk score stratified patients into low-, medium-, and high-risk groups with observed transfusion rates of 2.1%, 5.4%, and 15.1%, closely matching predicted probabilities of 2.1%, 5.8%, and 15.0%, respectively. Using a cut-off score of 4, specificity (91.7%) and negative predictive value (97.4%) were high, whereas sensitivity (37.7%) and positive predictive value (15.4%) were low.

This simple risk score, based on routinely available preoperative and intrapartum factors, may help identify patients at low risk for intraoperative transfusion, allowing more selective blood preparation, improved resource allocation, and more efficient utilization of blood products during cesarean delivery while supporting individualized clinical decision-making.