Major underestimation and overestimation of visual blood loss during cesarean deliveries: can they be predicted?

Purpose: The surgeons’ visual estimation is the most widely used method for estimating blood loss (BL) while performing cesarean deliveries (CDs). Major BL underestimation may adversely influence obstetric decision making, and result in delaying interventions. Major BL overestimation may result in unnecessary costly interventions. Therefore, we aimed to identify independent predictors for major BL underestimation and overestimation during CDs. Methods: All CDs performed between 11/2008 and 6/2016, in a university-affiliated hospital, were reviewed for demographic and surgical data, including the surgeons’ reported estimated BL (EBL). Calculated BL (CBL) was calculated by multiplying the calculated maternal blood volume by the percent of hematocrit decrease. Multivariate logistic regressions were performed to identify independent risk factors for major BL underestimation (CBL−EBL ≥ 400 ml) and overestimation (EBL−CBL ≥ 400 ml). Results: During the study period, 3655 CDs were analyzed, of which 420 met the criterion for major BL underestimation and 1214 for major BL overestimation. Urgent surgery (aOR = 2.83; 95% CI 2.06–3.89), general anesthesia (aOR = 2.39; 95% CI 1.71–3.33), and higher surgeon experience (aOR = 1.03; 95% CI 1.01–1.06) were found to be independent risk factors for major BL underestimation, while any previous CD (aOR = 0.47; 95% CI 0.33–0.67) decreased the risk of underestimation. Any previous CD (aOR = 1.29; 95% CI 1.05–1.58) and intra-abdominal adhesions (aOR = 1.37; 95% CI 1.11–1.70) were found to be independent risk factors for major BL overestimation, while urgent CD (aOR = 0.50; 95% CI 0.41–0.60) decreased the risk of overestimation. Conclusion: Various factors can predict major underestimation and overestimation of BL during CDs. Recognizing these factors can assist in the interpretation of visual EBL and improve obstetric decision making.