Preoperative Hemoglobin Levels and Risk of Postpartum Hemorrhage in Cesarean Delivery for Placenta Previa: A Retrospective Cohort Study

Background: Postpartum hemorrhage (PPH) remains a leading cause of maternal morbidity, particularly among women with placenta previa undergoing cesarean delivery. Preoperative hemoglobin (Hb) is a routinely available laboratory parameter that may reflect maternal hematologic reserve; however, its association with PPH risk in this population has not been well established. This study aimed to evaluate the relationship between preoperative Hb levels and PPH risk, assess the discriminative ability of preoperative Hb, and identify independent clinical risk factors for PPH in women undergoing cesarean section for placenta previa. Methods: This retrospective cohort study included 253 singleton pregnancies complicated by placenta previa who underwent cesarean section at Thai Binh Obstetrics and Gynecology Hospital between January 2024 and December 2025. Preoperative Hb levels were recorded prior to surgery. PPH was defined as estimated blood loss ≥1000 mL and/or the need for additional clinical intervention to achieve hemostasis. Receiver operating characteristic (ROC) analysis and multivariable logistic regression were performed to evaluate the association between preoperative Hb and PPH. Results: Among 252 cases with complete preoperative hemoglobin data, PPH occurred in 33 patients (13.1%). ROC analysis demonstrated modest discriminative ability of preoperative Hb for PPH (area under the curve [AUC] = 0.697; 95% confidence interval [CI]: 0.595–0.796), with an optimal cutoff of 118 g/L (sensitivity 69.7%, specificity 64.4%) identified using the Youden index. In multivariable analysis, higher preoperative Hb was independently associated with lower odds of PPH after adjustment for central placenta previa and history of previous cesarean delivery (adjusted odds ratio [aOR] = 0.95 per 1 g/L increase; 95% CI: 0.92–0.98; p = 0.001). Central placenta previa was independently associated with increased PPH risk (aOR = 2.48; 95% CI: 1.11–5.58; p = 0.028). After adjustment, history of cesarean delivery showed a positive association with PPH that did not reach statistical significance (aOR = 2.15; 95% CI: 0.95–4.87; p = 0.066). Conclusions: Lower preoperative Hb levels were independently associated with PPH in women undergoing cesarean delivery for placenta previa. Central placenta previa was likewise independently associated with increased PPH risk. Although preoperative Hb demonstrated only modest discriminative ability, it may serve as a useful adjunctive parameter for perioperative risk stratification when interpreted alongside established obstetric risk factors.