Abstract:Objective To explore the relationship between pre-pregnancy body mass index (BMI), weight gain during pregnancy and the success rate of vaginal trial delivery in pregnant women with trial of labor after previous cesarean delivery (TOLAC) after cesarean section, so as to provide a scientific basis for weight management during pregnancy and improving the success rate of vaginal trial delivery. Methods A total of 206 pregnant women with re-pregnancy after cesarean section in Drum Tower Hospital from January 2018 to December 2020 were selected as study subject and their general data was collected. According to the criteria, pre-pregnancy BMI grouping and weight gain grouping were carried out to compare the difference of pregnancy outcomes among different groups. Results There was no significant difference in age and gestational week among pregnant women with different pre-pregnancy BMI (P>0.05). The success rate of TOLAC in obesity group was the lowest (57.14%), and that in underweight group was the highest (100%). The success rate of TOLAC in excessive weight gain group was the lowest (27.91%), and the success rate of TOLAC in low weight gain group was the highest (96.92%). There was significant difference in TOLAC success rate among pregnant women with different pre-pregnancy BMI and weight gain during pregnancy after cesarean section (P<0.01). Conclusion Pre-pregnancy BMI and weight gain during pregnancy are closely related to the success rate of TOLAC. Controlling pre-pregnancy weight and weight gain during pregnancy within a reasonable range is of great significance to improve the success rate of TOLAC and reduce the rate of cesarean section.