Risk factors for postpartum hemorrhage according to the Robson classification in a low-risk maternity hospital

To evaluate the risk factors for postpartum hemorrhage (PPH) according to the Robson Classification in a low-risk maternity hospital.

We conducted retrospective cohort study by analyzing the medical records of pregnant women attended in a low-risk maternity hospital, during from November 2019 to November 2021. Variables analyzed were: maternal age, type of delivery, birth weight, parity, Robson Classification, and causes of PPH. We compared the occurrence of PPH between pregnant women with spontaneous (Groups 1 and 3) and with induction of labor (2a and 4a). Chi-square and Student t-tests were performed. Variables were compared using binary logistic regression.

There were 11,935 deliveries during the study period. According to Robson's Classification, 48.2% were classified as 1 and 3 (Group I: 5,750/11,935) and 26.1% as 2a and 4a (Group II: 3,124/11,935). Group II had higher prevalence of PPH than Group I (3.5 vs. 2.7%, p=0.028). Labor induction increased the occurrence of PPH by 18.8% (RR: 1.188, 95% CI: 1.02-1.36, p=0.030). Model including forceps delivery [x²(3)=10.6, OR: 7.26, 95%CI: 3.32-15.84, R² Nagelkerke: 0.011, p<0.001] and birth weight [x²(4)=59.0, OR: 1.001, 95%CI:1.001-1.001, R² Nagelkerke: 0.033, p<0.001] was the best for predicting PPH in patients classified as Robson 1, 3, 2a, and 4a. Birth weight was poor predictor of PPH (area under ROC curve: 0.612, p<0.001, 95%CI: 0.572-0.653).

Robson Classification 2a and 4a showed the highest rates of postpartum hemorrhage. The model including forceps delivery and birth weight was the best predictor for postpartum hemorrhage in Robson Classification 1, 3, 2a, and 4a.