Many pregnant moms with a history of a C-section(s) have encountered horror stories online about uterine ruptures while trying to make a birth plan for their next baby. When I was planning my own vaginal birth after Cesarean (VBAC), the words “uterine rupture” conjured up a vivid image of my C-section scar bursting open and my uterus spilling out of my abdomen. But what is a uterine rupture, and how should we approach this possibility when making a birth plan, particularly if that birth plan includes a VBAC?
What is uterine rupture?
Uterine rupture (UR) is defined by healthcare education and technology company StatPearls as the “complete division of all three layers of the uterus: the endometrium (inner epithelial layer), myometrium (smooth muscle layer), and perimetrium (serosal outer surface)” [1]. While most uterine ruptures happen to pregnant women, it is possible (though very rare) to have a uterine rupture due to uterine trauma (like in a car accident), infection, or cancer.
How often does uterine rupture occur?
Estimates of the number of uterine ruptures vary in medical research. A 2021 meta-analysis published in PLoS One found that about 5/1000 (0.5%) women with a uterus scarred by a previous C-section birth and 5/10,000 (0.0005%) without a previous C-section birth experience uterine rupture [2].
While uterine rupture is rare overall, a mother’s risk for rupture does increase with multiple C-sections, from approximately 1% for mothers with one C-section to 3.9% for mothers with more than one [1].
While uterine rupture is rare overall, a mother’s risk for rupture does increase with multiple C-sections, from approximately 1% for mothers with one C-section to 3.9% for mothers with more than one.
What are the signs of uterine rupture?
While some women may experience a “tearing” sensation followed by very painful contractions, the baby’s heart rate is the main indicator of uterine rupture (although only about 70% of ruptures affect the baby’s heart rate). The other indicators of uterine rupture are low maternal blood pressure, high heart rate, bloody urine, excess vaginal bleeding, and baby no longer moving down into the birth canal.
Uterine rupture is always a medical emergency
The nonspecific and inconsistent symptoms of uterine rupture can make diagnosis of uterine rupture difficult. However, with a mere 10-37 minutes before significant injury leading to death of the baby occurs, uterine ruptures are a medical emergency and timely recognition of the issue by the medical team is vital.
All uterine ruptures require infusion of IV fluids, and most require blood transfusion. Bladder injury is also common; 14-33% of women with uterine rupture will need a surgical removal of their uterus (hysterectomy) [1].
Maternal death and/or infant death (more likely), is also possible after uterine rupture, especially when diagnosis is delayed.
Reasons for uterine rupture
Uterine rupture in the developed world
The vast majority of uterine rupture cases in the developed world occur in women who have had at least one C-section, though about 1 in 10,000-25,000 deliveries by a woman with no prior C-section experience uterine rupture [1]. The four most common reasons for uterine rupture in an unscarred uterus are: uterine trauma; conditions resulting in a weak uterine wall (like gestational diabetes, macrosomia, or excess amniotic fluid); a prolonged induction or augmented labor with pitocin; or the overstretching of the uterine wall due to multiple babies in one pregnancy or from uterine fibroids.
Procedures like internal podalic and external cephalic version for attempting to flip breech babies also theoretically might increase the risk of uterine rupture by increasing the internal pressure in the uterus. However, in an older 2006 systematic review of 11 studies and 2,503 women who underwent external cephalic version, no ruptures were reported [3].
Uterine rupture in the developing world
By contrast, most women who experience uterine rupture in developing countries have not had a C-section. According to a 2022 study published in PLOS One, “the major cause [of uterine rupture] in these countries is obstructed labour, especially in rural areas. Other documented risk factors include grand-multiparity, injudicious use of oxytocin [pitocin] for labour augmentation, uterotonic drugs for induction of labour, instrumental delivery, poorly developed health system, and lack of facilities for timely referral to hospital in remote areas” [4]. Many of these cases are linked to home deliveries with poor obstetric practices, lack of emergency care facilities, and lack of awareness–all stemming from low socioeconomic conditions.
A quick note about pregnancy after previous uterine rupture
While rare, if a woman has had a previous uterine rupture without a hysterectomy and conceives again, the rate of repeat rupture is 33-100%, according to several case series from other countries. For this reason, OB/GYNs and maternal fetal medicine specialists recommend scheduling a Cesarean delivery between 36-37 weeks gestation, before spontaneous onset of labor, for pregnant women who’ve experienced a prior rupture [1].
How often does uterine rupture result in maternal or neonatal death?
When a mother and/or baby dies during a uterine rupture, it is known as “catastrophic” uterine rupture. Thankfully, rates of either the mother or baby dying due to a rupture are relatively low. The rate of death for babies (either during labor or up to four weeks after birth) is 6%, and for babies born at term, the rates are 0-2.8%. Using the statistic of about 0.7% risk of rupture during a spontaneous labor after C-section, the absolute risk of a catastrophic rupture is between 0.02-0.04%, or between 1 in 2,380 VBACs to 1 in 5,100 VBACs resulting in the death of the baby. However, as VBAC Facts acknowledges, the data on neonatal mortality from uterine rupture is generally considered low quality, meaning that it’s difficult to know how accurate it is.
One 2022 study published in BMC Pregnancy and Childbirth found that out of 209,112 deliveries in Shanghai, China over an 8-year period, there were only 41 cases of rupture [5]. Out of those 41 uterine ruptures, 16 led to mother and child health complications, and 3 led to the death of the baby. No deaths of the mother were reported. Out of the 41 uterine rupture cases, 38 had a uterus scarred by a previous C-section, and three had an unscarred uterus.
Why are mothers with an unscarred uterus more likely to die from uterine rupture?
While having a uterus scarred by a previous C-section clearly makes one more susceptible to uterine rupture, according to StatPearls, the mortality rate for both babies and mothers with an unscarred uterus are higher than those with a scarred uterus (about a 10% mortality rate each for mother and baby, compared to 0.1% for mother and 2% for baby with a scarred uterus) [1]. Overall, uterine rupture in an unscarred uterus is associated with higher rates of blood loss, hysterectomy, bladder injury, and death for the mother as well as hemorrhage, seizure, brain injury, and death for the baby [1].
This may be in part because women with an unscarred uterus undergo minimal monitoring for rupture compared to women undergoing a trial of labor after Cesarean (making the previously mentioned “non-specific” symptoms harder to detect). Additionally, women who are attempting a VBAC usually give birth in a hospital with an operating room available in case of emergency C-section (and, potentially, hysterectomy).
Uterine rupture: What you need to know
The percentage of women with a history of C-sections experiencing uterine rupture are low, and the instances of catastrophic uterine rupture even lower. That said, ruptures are serious, and understanding what they are and how they occur is important. In part two of this Primer, we’ll take a closer look at the various risk factors for uterine rupture and how they may be mitigated.
