As we know from Part I of this article, uterine rupture is when all three layers of the uterus completely divide, typically (though not always) during labor. Uterine rupture is a true medical emergency that requires immediate intervention. While rare, uterine rupture can result in bladder injury, a hysterectomy, and even maternal and/or infant death if it occurs in pregnancy. Understanding the risk factors for this serious medical situation is important, especially for expectant mothers hoping for a vaginal birth after Cesarean section (VBAC). Here, we look at the contributing risks of uterine rupture, how those risks might be lowered, and safe labor practices.
Terms to know when talking about uterine rupture
Before diving further into this topic, let’s get some of our verbiage straightened out:
- TOLAC: “Trial of labor after Cesarean;” when a mother attempts to give birth vaginally after a prior Cesarean section (VBAC).
- CBAC: “Cesarean birth after Cesarean;” when an attempted VBAC was deemed unsafe and a C-section was performed instead.
- VBAC: “Vaginal birth after Cesarean;” when a mother successfully delivers her baby vaginally after previously having a C-section.
In the developed world, C-sections create the greatest risk for future uterine rupture
In the developed world, the women facing the largest risks for a uterine rupture are those undergoing a trial of labor after Cesarean (TOLAC), with the rate of rupture 15-30 times greater than for women undergoing another C-section. Women attempting a TOLAC with a midline C-section scar (in the shape of an inverted T, typically used when the surgeon needs more room to get the baby out–like in this case where the mother had large uterine fibroids) are 2-3 times more likely than those women with a low transverse incision more commonly found in elective Cesarean deliveries today [1][2].
According to StatPearls, “while a successful vaginal birth resulting from TOLAC is associated with less [risk] than a scheduled Cesarean delivery, a failed TOLAC that ends in Cesarean delivery is associated with more morbidity than a scheduled Cesarean delivery” [1]. Because of the risk of a TOLAC to mother and baby, most hospitals will have healthcare professionals in obstetrics, anesthesia, pediatrics, and operating room personnel prepared in the chance that an emergency C-section is required.
Number of previous Cesareans
The number of previous Cesareans is also a risk factor for uterine rupture. Some research suggests that for women with one previous C-section, the rate of rupture is about 1%, while women with two or more C-sections have an increased chance of 3.9% [1]. Notably, the rate of both first time and repeat C-sections continues to increase in the United States—in 1996, 20.7% of births were C-sections, while in 2021, 32.1% of all births were via C-section [4].
The good news: One successful VBAC begets another
Encouragingly, however, after a first successful VBAC, future VBAC success increases with each subsequent delivery, while risk for uterine rupture decreases with each successful delivery. For example, one 2008 study published in Obstetrics & Gynecology followed 13,532 women over multiple VBAC deliveries, and found that VBAC success “increased with increasing number of prior VBACs: 63.3%, 87.6%, 90.9%, 90.6%, and 91.6% for those with 0, 1, 2, 3, and 4 or more prior VBACs, respectively. The rate of uterine rupture decreased after the first successful VBAC and did not increase thereafter: 0.87%, 0.45%, 0.38%, 0.54%, 0.52%” [3].
Induction poses the next highest risk for rupture
After having a previous Cesarean delivery, the next highest risk factor for uterine rupture is induced (synthetically initiated) or “augmented” labor, through medications like synthetic oxytocin (pitocin) and/or prostaglandins (Cytotec or misoprostol). Prostaglandins are used for softening the cervix and stimulating uterine contractions, while pitocin stimulates the uterus to contract after the cervix has already ripened.
An old study published in the New England Journal of Medicine found that out of a group of 20,095 women pregnant with their second child with a C-section first birth, those who were induced with prostaglandins (misoprostol) had a significantly higher risk of uterine rupture.
By the numbers, 1.6 /1000 women who had a second elective C-section had uterine rupture, 5.2/1000 with spontaneous onset of labor had uterine rupture, 7.7/1000 women induced with just oxytocin had uterine rupture, and 24.5/1000 women with misoprostol induced into labor had a uterine rupture [5].
Importantly, induction rates in the United States have tripled in the past 30 years, and induction itself may be a risk-factor for C-section. This underscores the need for labor and delivery departments to follow the science when it comes to birth, to better understand and communicate to women the real risks of pitocin, to only induce women when it is strictly medically indicated, and to offer women alternative forms of induction.
Importantly, induction rates in the United States have tripled in the past 30 years, and induction itself may be a risk-factor for C-section.
Uterine rupture risk is relatively higher in women who have prostaglandin-induced labor
Further underscoring the risks of inducing and/or augmenting labor, a more recent population based retrospective cohort study published in the American Journal of Obstetrics and Gynecology followed 296,614 women undergoing a TOLAC and found that “60% were not induced, 21% were augmented, and 19% were induced. Uterine rupture rates were 0.18%, 0.34%, 0.45% in the non-induced, augmented, and induced groups respectively” [6].
Importantly, even women without a previous C-section showed a statistically higher risk of uterine rupture when using prostaglandins and pitocin compared to women whose labour started naturally. Fifty-one out of 1,317,967 women with uteruses unscarred by previous C-sections experienced uterine rupture. In more manageable numbers, that equals about 1 out of 26,000 births, which means risk of uterine rupture with induced and/or augmented labor is quite rare, but it is still a 48-fold increase compared to unscarred women in spontaneous labor [6].
Risk of uterine rupture with induced and/or augmented labor is quite rare, but it is still a 48-fold increase compared to unscarred women in spontaneous labor.
Is there any way to lower the risk of rupture for women trying for a VBAC?
Protective effect of previous vaginal delivery
Fascinatingly, if you’ve already had a previous vaginal delivery, even if it was before your C-section, chances of experiencing a uterine rupture are significantly lowered. A prior vaginal delivery seems to indicate that the uterus can withstand the stresses of labor and delivery without complications. Additionally, each subsequent labor tends to be shorter and more efficient, and the cervix may be more responsive and dilate faster.
What’s more, with subsequent deliveries, you may be less likely to need induction or augmentation of labor because your pelvis has already successfully shifted (at least) once to accommodate the baby’s passage through, which may help prevent excessive stretching of the uterus. In women with successful VBAC, subsequent labor and deliveries likewise shows that the uterine scar tends to hold firm against the intense contractions and forces of labor [6]
A 12-year-long study published in the American Journal of Obstetrics and Gynecology followed 3,783 women all with one previous C-section and delivered via TOLAC. 1,021 had at least 1 prior vaginal delivery. Researchers found that the rate of uterine rupture in the women without previous vaginal delivery was 1.1%, while the women with at least one previous vaginal birth was 0.2% [7].
Safe labor practices
Remember from above that a successful VBAC has fewer complications than a scheduled repeat Cesarean; however, when a TOLAC with the goal of VBAC “goes bad,” the risks are higher than simply having a scheduled repeat Cesarean. Uterine rupture is the most significant risk of a failed TOLAC. Because of this risk, attempting a TOLAC outside of the hospital needs to be discussed very seriously with your doctor or midwife.
Whether you deliver in a hospital, birth center, or at home, midwives offer professional medical assistance and statistically women who deliver with a midwife (or even a doula) show lower rates of C-section. According to The Commonwealth Fund, families who use midwives during pregnancy, labor, and delivery have lower maternal and fetal deaths, more efficient use of health resources leading to a decrease in C-sections, epidurals, and instrument-assisted births (think vacuum or forceps). Having a midwife or a doula, even in a hospital setting, can ensure that the doctor and medical staff respect your wishes regarding your birth plan allowing you to focus on bringing your baby earth-side while keeping you and baby safe.
The bottom line on uterine rupture
Uterine rupture, while very rare, is a medical emergency. Rupture occurrence continues to increase as C-section and induction rates around the world increase. There are ways to minimize risk of uterine rupture–avoiding artificial labor induction or augmentation, avoiding multiple elective C-sections, and having had a prior vaginal delivery improve the odds of avoiding ruptures. In short, helping first-time moms have healthy, safe, spontaneous (as opposed to induced) vaginal deliveries might be the very best way to mitigate the risk of uterine rupture in subsequent pregnancies.
In short, helping first-time moms have healthy, safe, spontaneous (as opposed to induced) vaginal deliveries might be the very best way to mitigate the risk of uterine rupture in subsequent pregnancies.
If you’ve had a previous C-section and plan for a VBAC, talk to your medical clinician about your risk status–as long as it’s safe for you and your baby, I can attest that getting your first VBAC can feel like one of the greatest accomplishments of your life!
References:
[1] Togioka BM, Tonismae T. Uterine Rupture. [Updated 2023 Jul 29]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2025 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK559209/ [2] Almusalam MM, Badawi A, Bushaqer N. Are Deliveries by Inverted T-Incision on the Rise Due to Fibroids?: A Case Report. Cureus. 2022 May 6;14(5):e24781. doi: 10.7759/cureus.24781. PMID: 35677011; PMCID: PMC9167637. [3] Mercer BM, Gilbert S, Landon MB, et al. National Institute of Child Health and Human Development Maternal-Fetal Medicine Units Network. Labor outcomes with increasing number of prior vaginal births after cesarean delivery. Obstet Gynecol. 2008 Feb;111(2 Pt 1):285-91. doi: 10.1097/AOG.0b013e31816102b9. PMID: 18238964. [4] Stephenson J. Rate of First-time Cesarean Deliveries on the Rise in the US. JAMA Health Forum.2022;3(7):e222824. doi:10.1001/jamahealthforum.2022.2824 [5] Lydon-Rochelle M, Holt VL, Easterling TR, Martin DP. Risk of uterine rupture during labor among women with a prior cesarean delivery. N Engl J Med. 2001 Jul 5;345(1):3-8. doi: 10.1056/NEJM200107053450101. PMID: 11439945. [6] Risk of labor induction or augmentation on uterine rupture during trial of labor after cesareanMuller, Benjamin M. et al. American Journal of Obstetrics & Gynecology, Volume 226, Issue 1, S768 [7] Zelop CM, Shipp TD, Repke JT, Cohen A, Lieberman E. Effect of previous vaginal delivery on the risk of uterine rupture during a subsequent trial of labor. Am J Obstet Gynecol. 2000 Nov;183(5):1184-6. doi: 10.1067/mob.2000.109048. PMID: 11084564.
