Gestational Diabetes Lowers VBAC Odds

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Thankfully I still have a good chance of getting my VBAC.

LOS ANGELES — Women attempting a vaginal birth after a previous cesarean delivery are more likely to need another C-section if they have gestational diabetes, but their chances of a successful vaginal birth are still good, Dr. Dominic Marchiano said.

Vaginal birth after a prior cesarean section (VBAC) succeeded in 68% of women with gestational diabetes and in 75% of women without gestational diabetes in a retrospective study of 25,079 pregnant women with a history of C-section. The study participants were seen at 16 community and university hospitals in a 4-year period, Dr. Marchiano reported during the annual meeting of the American College of Obstetricians and Gynecologists.

Stated another way, women with gestational diabetes were 23% less likely to have a successful VBAC.

The 6% of women who had gestational diabetes were less likely to attempt a trial of labor after a previous C-section: Only 40% of the 1,465 women with gestational diabetes attempted VBAC, compared with 54% of the 23,614 women without the disorder, said Dr. Marchiano of the University of Pennsylvania, Philadelphia.

The results of the study may have been affected by factors in the preselection of patients attempting VBAC such as prior pregnancy history, estimated fetal weight, or physician and patient preferences, he acknowledged.

Other limitations to the study include the inability to control for factors involved in the induction of labor, Dr. Marchiano said. Investigators also had no information about physicians’ thresholds for halting a trial of labor already in progress to perform a C-section.

For the patients who attempted VBAC, the investigators controlled for confounding variables including birth weight, maternal age, tobacco use, chronic hypertension, and pregestational diabetes. More women in the gestational diabetes group had chronic hypertension. Differences between groups in gravidity, maternal age, and gestational age were statistically different but not clinically significant.

Birth weights were similar between groups, “so our finding of different success rates in patients with or without gestational diabetes is not attributable to higher birth weights among the diabetics,” he said.

Gestational diabetes occurs in 2%-5% of pregnancies and is associated with macrosomia and increased use of C-section. ACOG does not recommend doing a C-section based simply on the presence of gestational diabetes.

The only previous study to examine the combination of VBAC and gestational diabetes included fewer women seen at a single institution.

Investigators in that study also concluded that, although the likelihood of C-section is slightly elevated in women with gestational diabetes, VBAC remains an acceptable alternative in this population (Am. J. Obstet. Gynecol. 184[6]:1104-07, 2001).

Compared to this earlier study, “ours is a larger and more diverse patient population. We believe our data are applicable to most practice scenarios,” he said.

Physicians should counsel women with gestational diabetes that they have a slightly higher risk of VBAC failing but that “the overall success rate is still favorable,” Dr. Marchiano said.


4 Comments (+add yours?)

  1. erinmidwife
    Aug 11, 2010 @ 03:32:11

    Hi, just stumbled across your blog 🙂 Blessings to you in your VBAC journey.

    We would really need to see the original study to look at the numbers.
    “Only 40% of the 1,465 women with gestational diabetes attempted VBAC…..
    The results of the study may have been affected by factors in the *preselection* of patients attempting VBAC such as prior pregnancy history, estimated fetal weight, or physician and patient preferences, he acknowledged.”

    This is significant because what is saying is that the majority of VBAC/GDM women in the sample size did not attempt to birth vaginally, for reasons we do not know. (So 68% of the 40% who planned a VBAC actually had one?). Perhaps many of the VBAC women had hoped for vaginal births but were not “allowed” or were discouraged by their care providers attitudes toward VBAC.

    A high “estimated fetal weight” is a ubiquitous and garbage label given to women all the time as rationale for induction and repeat cesarean. Have you seen this wonderful video?

    In my experience the highest likelyhood for VBAC success (GDM or not) is to find a care provider whose walks the talk (hire a midwife). Many OBs unfortunately pay some amount of lip service to VBAC, then bait and switch you at term. Oh, your baby is too big, Oh you don’t have enough fluid, Oh let’s just not add any “risk”, and so on. Ask for their actual stats on VBAC.
    Secondly, avoid induction and any augmentation (pitocin) unless truly necessary (which is rare), third, hire an experienced doula if you are going to birth in the hospital and fourthly, don’t go in to the hospital until you labor is well underway.


  2. erinmidwife
    Aug 12, 2010 @ 03:10:31


  3. The WellRounded Mama
    Sep 16, 2010 @ 18:46:07

    If you look at the final published study, the numbers change slightly and more favorably. See Marchiano 2004, AJOG.

    What’s most striking, though, is the rate of VBACs in spontaneous labor (82%) vs those with induced/augmented labor (65%). Alas, they did not report separately on induced labors vs. augmented labors, which would probably have meant even more dramatic differences.

    However, in their logistic regression model, the odds ratio for spontaneous labor GD VBAC success was 1.0. For augmented labor, it was 0.61, and for induced labor, the odds ratio was 0.39. That’s pretty striking.

    The critical issue in GD and VBAC is LETTING THE MOTHER LABOR SPONTANEOUSLY. In my many years in the International Cesarean Awareness Network (, I have observed over and over again how a high rate of induction is the main barrier in GD moms wanting VBACs.

    VBAC is not impossible with induced labors, of course, but the rates are VERY consistently lower. Since so many women with GD are induced and many docs are fearful of “letting” women go later with GD, the impulse towards induction seems to be the greatest barrier preventing women with GD from getting a VBAC.

    Most of the women I know who have had VBACs with GD have found providers supportive of letting them labor spontaneously, without major time limits of going into labor by xx weeks. Finding those providers, however, is the hardest part of the journey.


  4. happymommy85
    Feb 04, 2013 @ 21:00:51

    Wow thank you guys for these very helpful comments!! 😀


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