Gynecology World Conference 2026

Abstract

Objective: This study aimed to analyze the obstetricians’ accuracy of visual estimation of blood loss both in Cesarean Sections (CS) and Vaginal Deliveries (VD) and to identify clinical factors which show a universal association with the occurrence of early postpartum hemorrhage (PPH), regardless of the final route of delivery.

Methods: This prospective observational cohort study included 958 women in singleton pregnancies, undergoing elective or emergency Cesarean Section (CS, n=473) and spontaneous or induced Vaginal Delivery (VD, n=485). Blood loss was evaluated using two methods: subjective visual estimation by the operator (sEBL) and an objective mathematical formula (fEBL). The relative estimation error was calculated using the formula: (sEBL - fEBL) / fEBL. The incidence of PPH was analyzed under two definitions: a group-specific definition (≥1000 mL for CS / ≥500 mL for VD) and a unified definition (≥1000 mL for both modes). Univariate and multivariate logistic regression analyses were conducted to evaluate potential PPH risk factors.

Results: Visual blood loss estimation (sEBL) showed high accuracy in CS (median relative error: +5.4%, 95% CI: 0.8% to 12.0%), but a severe underestimation in VD (median relative error: -55.1%, 95% CI: -58.2% to -52.1%, p < 0.001). Under the group-specific definition, PPH incidence was higher in VD than CS (6.2% vs 2.7%, p < 0.001), but under the unified definition (>=1000 mL), the difference was non-significant (2.3% vs 2.7%, p = 0.68). In univariable, macrosomia (OR 4.79, p < 0.001) was identified as a significant risk factor for PPH, while gravidity (OR 0.65, p = 0.073) and parity (OR 0.52, p = 0.060) showed a non-significant protective trend. No significant risk or protective effect was found for age groups, pre-term delivery (OR 0.67, p = 0.7), BMI categories (25-29.9: OR 0.92, p = 0.9; 30-39.9: OR 1.73, p = 0.3; >40: OR 0.00, p > 0.9), night shift work (OR 0.45, p = 0.2), or spinal anesthesia (OR 1.29, p = 0.7). Likewise, multivariable regression identified macrosomia as the only independent risk factor for PPH (OR 5.14, 95% CI: 1.87-13.0, p < 0.001). Age groups, pre-term delivery (OR 0.87, p = 0.9), gravidity (OR 0.86, p = 0.7), parity (OR 0.60, p = 0.3), BMI categories (25-29.9: OR 0.91, p = 0.9; 30-39.9: OR 1.97, p = 0.2; >40: OR 0.00, p > 0.9), night shift work (OR 0.43, p = 0.2), and spinal anesthesia (OR 0.98, p > 0.9) remained non-significant.

Conclusions: Obstetricians significantly underestimate blood loss during vaginal deliveries by more than half, while visual estimation during Cesarean sections is relatively precise. The perceived difference in PPH rates between delivery modes is driven by definition thresholds; when a unified 1000 mL threshold is applied, the incidence of PPH is comparable between CS and VD. Fetal macrosomia serves as a universal independent risk factor for early PPH (OR 5.14, p < 0.001) regardless of the final route of delivery.