Diet-controlled gestational diabetes mellitus does not influence the success rates for vaginal birth after cesarean delivery

Objective: We sought to determine whether women with diet-controlled gestational diabetes mellitus who attempt vaginal birth after cesarean delivery are at increased risk of failure, when compared with their non-diabetic counterparts. Study design: We identified 13,396 women who attempted vaginal birth after cesarean delivery among 25,079 pregnant women with a previous cesarean delivery who were delivered between 1995 and 1999 at 16 community and university hospitals. Analysis was limited to 9437 women without diabetes mellitus and 423 women with diet-controlled diabetes mellitus who attempted vaginal birth after cesarean delivery with a singleton gestation and 1 previous low-flap cesarean delivery. Data that were collected by trained abstractors, included demographics, medical history, and both pregnancy and neonatal outcomes. Multivariable logistic regression analysis was performed to determine an adjusted odds ratio for vaginal birth after cesarean delivery success among women with diet-controlled gestational diabetes compared with women with no diabetes mellitus. We controlled for birth weight, maternal age, race, tobacco, chronic hypertension, hospital settings, labor management, and obstetric history. Results: Forty-nine percent of the women with gestational diabetes mellitus and 67% of the women with no diabetes mellitus attempted vaginal birth after cesarean delivery. The success rate for attempted vaginal birth after cesarean delivery among gestational diabetic women was 70%, compared with 74% for non-diabetic women. We found that gestational diabetes mellitus is not an independent risk factor for vaginal birth after cesarean delivery failure. The relative risk for vaginal birth after cesarean delivery success in women with gestational diabetes mellitus compared with women without gestational diabetes mellitus was 0.94 (95% CI, 0.87-1.00). After an adjustment was made for confounding, the odds ratio for success with gestational diabetes mellitus was 0.87 (95% CI, 0.68-1.10). Conclusion: Women with diet-controlled gestational diabetes mellitus who were carrying singleton fetuses who had no more than 1 previous low flap cesarean delivery should be counseled that their disease does not decrease their chances for a successful vaginal birth after cesarean delivery. Among diet-controlled diabetic women, the overall success rate for vaginal birth after cesarean delivery remains acceptable, and attempted vaginal birth after cesarean delivery should not be discouraged solely on the basis of gestational diabetes mellitus.