The association between obesity and the success of trial of labor after cesarean delivery (TOLAC) in women with past vaginal delivery.

Objectives: To evaluate the effect of overweight (body mass index; BMI 25.0-29.9 kg/m), and obesity (BMI>30 kg/m), on the success of trial of labor after cesarean delivery (TOLAC), with consideration of successful past vaginal birth.

Methods: This retrospective cohort study was performed using electronic database of obstetrics department at a university-affiliated tertiary medical center. All women admitted for TOLAC at 37-42 weeks of gestational age, carrying a singleton live fetus at cephalic presentation, with a single previous low segment transverse cesarean delivery between 1/2015 and 5/2021 were included. Primary outcome was the rate of cesarean delivery during labor, and subgroup analysis was performed for the presence of past vaginal birth.

Results: Of the 1200 TOLAC deliveries meeting the inclusion criteria, 61.9 % had BMI in the normal range, 24.6 % were overweight (BMI 25.0-29.9 kg/m), and 13.4 % were obese (BMI of 30 kg/m and over). Using a multivariate analysis, BMI≥30 kg/m was associated with increased risk of cesarean delivery compared to normal weight. However, in the subgroup of 292 women with a history of successful vaginal birth BMI did not affect TOLAC success.

Conclusions: BMI does not affect the success of TOLAC in women with previous vaginal birth. This information should be considered during patients counselling, in order to achieve a better selection of mode of delivery and higher patients' satisfaction.