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SAN FRANCISCO -- Obstetricians performing cesarean sections may be able to determine when postpartum hemorrhage (PPH) is brewing simply by palpating the uterus, a researcher said here.

Low scores on a uterine tone test performed 12 minutes after delivery were strongly associated with PPH onset in a prospective study, with an area under the receiver operating characteristic curve (AUC) of 0.81, according to James Xie, MD, of Stanford University in California.

Each 1-point decrement in tone score raised the risk of major PPH by 79%, he told attendees at the American Society of Anesthesiologists annual meeting.

The study proved that performing the tone test was feasible during routine C-section deliveries, Xie said. Whether it can actually improve outcomes, however, remains to be determined, as the researchers didn't track them in this preliminary study. Still, to the extent that forewarned is forearmed, it's a good bet that the study's findings will be a step in the right direction.

As Xie explained, PPH is a leading cause of maternal mortality and morbidity. Some 70%-80% of PPH cases result from uterine atony, that is, failure to contract during and after delivery. This in turn means that blood vessels serving the placenta remain open, with potentially catastrophic blood loss a consequence.

Obstetricians can detect atony fairly easily by palpating the uterine fundus. The question for Xie and colleagues was whether this could be done and recorded routinely in ordinary practice. So, they arranged with Stanford-area ob/gyn services to have tone tests taken at regular intervals during C-section deliveries.

Specifically, anesthesiologists in the delivery suite were prompted by their electronic records system to ask the obstetrician to perform tone tests at 2, 7, and 12 minutes after delivery, scoring them on a 0-10 scale in which 0 reflects "profound" atony and 10 indicates perfect tone. Results were then compared with quantitative blood loss (QBL) and need for transfusion.

A total of 1,004 deliveries in 2022 were enrolled in the study. All but 10 provided enough data to be included in the analysis.

Documentation of tone score was confirmed for 87%, 97%, and 98% of tests that performed at 2, 7, and 12 minutes, respectively. Thus, said Xie, it was clearly possible to do the tests and record them in normal practice.

In terms of PPH prediction, it appeared that the 12-minute score was most informative, and a tone score of 6 was the best cutoff that predicted PPH. Of the 994 evaluable deliveries, 179 (18%) had scores of 6 or below at minute 12, and some 80% of these cases resulted in hemorrhage. Transfusions were less common, provided in about 40% of deliveries with tone scores of ≤4 and 15% of those with scores of 5 or 6.

That cutoff provided a positive predictive value of 77% for any hemorrhage (QBL >1 L). For major hemorrhage (QBL >1.5 L), the positive predictive value was 46%, and it was 25% for predicting need for transfusion.

Conversely, scores of 8 and above had high negative predictive values at all three readings, in excess of 95% for major hemorrhage and transfusion.

Scores of 7 at minute 12, which were recorded for about 20% of the cohort, were therefore indeterminate.

The next step, Xie said, is to "assess whether using [low tone score] to trigger implementation of hemorrhage care bundles improves patient outcomes."

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