Second-trimester anthropometric estimators of cesarean section: the agreement between body roundness index, body mass index, body fat percentage, and waist circumference.

Purpose: To explore the relationships between second-trimester anthropometric obesity indicators and cesarean section (CS).

Methods: A retrospective study was conducted at West China Second University Hospital, utilizing electronic health records from 15,304 pregnant women who received routine prenatal care and delivered between January 2021 and June 2022. Second-trimester anthropometric indicators, including body roundness index (BRI), body mass index (BMI), body fat percentage (BFP), and waist circumference (WC), were measured using bioelectrical impedance analysis (BIA). Logistic regression models were employed to assess the associations between these indicators and CS risk, with additional subgroup analyses based on maternal age and fetal sex.

Results: The mean maternal age was 30.13 years. After adjusting for covariates, BRI (OR 1.22, 95%CI 1.15-1.30), BMI (OR 1.07, 95%CI 1.05-1.08), BFP (OR 1.03, 95%CI 1.02-1.04), and WC (OR 1.02, 95%CI 1.01-1.03) were all significantly associated with CS. Stratified analyses based on maternal age and fetal sex further confirmed these independent associations.

Conclusion: Second-trimester BRI, BMI, BFP, and WC were all significantly associated with CS risk, with BRI potentially demonstrating the strongest independent correlation. An integrated approach incorporating BMI and WC is recommended for CS risk, particularly in time-sensitive or resource-limited settings. The effect of anthropometric changes during pregnancy on CS may be explored in the future.