No uterine rupture at VBAC TOL if birth weight less than 2900 and no use of medical induction or augmentation of labor

Abstract

Since the causes of uterine rupture at vaginal birth after cesarean (VBAC) trial of labor (TOL) are known although to date denied due to medicolegal fears, I was very curious to read the article: Prediction of uterine rupture in singleton pregnancies with one prior cesarean birth undergoing TOLAC: A cross-sectional study in the November 2024 issue of your journal.¹

The authors write in their Conclusions they “wish there was a more robust prediction model for uterine rupture in TOLAC.” This is a curious goal in light of the fact there already exists a robust prediction model for VBAC trial of labor after cesarean (TOLAC) uterine rupture: To eliminate VBAC TOL uterine rupture, deliver term birth weights of less than 2900 gm without induction or augmentation. Not a single case of TOL uterine rupture has been documented where uterine rupture is clearly defined, induction or augmentation are not used at all and the birth weight is 2950 kg or less. It is unfortunately also true that there is an obvious motivation to underreport the use of medical induction and Pitocin augmentation after uterine rupture occurs.

The US birth certificate database used in this study is not a proper tool to examine relatively rare and sometimes undocumented outcomes like uterine rupture. But there is enough data to prove that not inducing and augmenting where the birth weight is under 2950 eliminates uterine rupture in vaginal births after one cesarean (VBA1C) labors. It is impossible to know if the data on VBA1C also apply to women after multiple cesareans due to a lack of reporting on uterine rupture after two or more cesareans in the absence of medical induction or augmentation. (Anecdotally, my experience with 105 VBA2C supports that it is true for women after multiple cesareans.) In hospitals reporting 25% induction and another 25% Pitocin augmentation rates at VBA1C TOL, uterine rupture occurs at a rate of 10 per 1000 VBA1Cs.^2-6 In the absence of induction and augmentation, 2 per 1000 VBA1C uterine rupture occur and zero uterine rupture occurred with birth weight under 2977 gm.⁷ From the above research, it can be derived that 10/1000–2/1000 = 8/1000 or 80% of VBA1C uterine rupture in labor is the result of medical induction and/or augmentation at VBA1C labor and the other 20% is due to birth weights over 3 kg. To eliminate VBA1C uterine rupture, deliver term birth weight less than 2900 gm without induction or augmentation. Term birth weight under 2900 are achieved by eating low glycemic diets and regular exercise such as walking for 1 to 2 h per day.⁸

Even using a relatively unreliable database copied from birth certificate data and not tested for accuracy, in the November 2024 study, 70% of uterine ruptures were caused by induction or augmentation of labor. The time is long overdue to teach women that a low carb diet and daily exercise produces a final birth weight of 2900 gm or less at term every time, and will ELIMINATE all uterine rupture in the common VBA1C TOL as long as the woman refuses induction and augmentation. If the researchers who wrote this paper go back and look at their data, it will confirm this point. They must extract the birth weight of the 257 uterine ruptures that were not induced or augmented, eliminate those confounded by induction, augmentation, non-low transverse scar types (non-LTCS), multiple previous uterine scars, unclear definitions of uterine rupture, and high risk pregnancies such as diabetics, pre-eclamptics, heavy smokers, and other risky lifestyles, and report the birth weights of those births. I look forward to reading their future article containing this data.