Predictors of Maternal Morbidity among Individuals at Low Risk of Postpartum Hemorrhage

This study aimed to identify predictors for maternal morbidity among individuals categorized as low-risk for postpartum hemorrhage (PPH) according to American College of Obstetrics and Gynecology (ACOG) Practice Bulletin (no.: 183).

A retrospective cohort study of all singleton births between March 2020 and February 2022 at a Level IV maternity center. Individuals deemed at medium- or high-risk for PPH according to the ACOG risk stratification and those with missing data were excluded from the main analysis. Individuals with the composite maternal hemorrhagic outcome (CMHO) were compared with those without. Variables previously associated with maternal morbidity yet absent from the ACOG stratification were examined as potential predictors of the CMHO. Possible predictors were identified using a multivariable logistic regression and further assessed with a receiver operating characteristic curve (ROC).

Out of 8,623 deliveries, 3,472 (40.3%) met the inclusion criteria. Among them, 175 (5.0%) had a CMHO. Individuals with the composite outcome were older, had a higher body mass index, and had higher rates of Hispanic race/ethnicity, diabetes, postterm pregnancy, scheduled cesarean delivery, and neonatal birth weight ≥ 4,000 g. The combination of ≥ 2 risk factors among low-risk patients, present in 16%, was associated with a similar CMHO rate compared with those at medium PPH risk by the ACOG criteria. The combined presence of ≥ 4 factors was associated with a CMHO rate of 36% and yielded a 10.47 positive likelihood ratio (95% confidence interval [CI]: 3.55-30.90). The area under the curve for the ROC curve of the final model was 0.63 (95% CI: 0.62-0.65).

Among low-risk PPH patients, several risk factors with low predictive value flagged roughly one out of six with morbidity similar to medium risk.

· Five percent of individuals categorized as low-risk for PPH have hemorrhagic morbidity.. · Several predictors of morbidity were identified.. · Low-risk patients with ≥ 2 predictors had similar morbidity to patients with a moderate PPH risk..