Uterine Tone Numeric Rating Score as an Early Indicator of Major Postpartum Hemorrhage during Cesarean Delivery: A...

Postpartum hemorrhage (PPH) is the leading preventable cause of maternal mortality. Most PPH cases are caused by uterine atony, which is inconsistently defined in clinical care. The electronic health record was used to prompt communication between the anesthesia and obstetric care teams about uterine tone using a validated 11-point numeric rating scale (NRS) at 0, 5, and 10 min after placental delivery for all cesarean deliveries at our institution. The primary hypothesis was that lower uterine tone NRS would be strongly associated with progression to major PPH.

This was a single-center, prospective observational study conducted over a 1-yr period. The primary predictor was the 0 to 10 uterine tone NRS recorded 10 min after placental delivery, and the primary outcome was major PPH, defined as quantitative blood loss greater than or equal to 1,500 ml. Area under the receiver operating characteristic curves were created, and the relative risk of major PPH for each 1-point change in the tone score was estimated. Key secondary outcomes analyzed included associations between tone scores, PPH, and blood transfusion.

A total of 1,599 consecutive cesarean deliveries were performed by obstetricians from academic (39.3%), county public health (21.1%), and private practice (38.8%) services. Major PPH complicated 9.9% and transfusion 6.7% of cesarean deliveries. Uterine tone NRS was documented at 0 min after placental delivery in 91.6%, 5 min in 97.4%, and 10 min in 97.0% of cesarean deliveries. The 10-min NRS was a strong predictor of major PPH, with an area under the receiver operating characteristic of 0.78 (95% CI, 0.73 to 0.82). Each 1-point decrease in NRS increased the risk of major PPH by 71% (95% CI, 0.58 to 0.86). A 10-min uterine tone NRS less than or equal to 6 had high positive predictive value for major PPH (32.9%), as well as PPH (64.2%) and transfusion (20.6%).

Standardized uterine tone assessments on a 0 to 10 scale are feasible to implement and strongly associated with progression to major PPH and blood transfusion. Future studies should investigate whether implementation of PPH interventions based on uterine tone NRS can reduce major PPH and hemorrhage-associated morbidity.