Vaginal birth after cesarean (VBAC) is a safe alternative to a routine repeat cesarean and is recommended as an option by the world’s leading professional associations of obstetricians and gynecologists. Evidence tells us that about 70 to 75 percent of women who labor for a VBAC give birth safely. However, for about 1 in 200, the cesarean scar on the uterus may separate. A uterine scar rupture is a serious complication that can occur during pregnancy or labor and is characterized by a tear in the wall of the uterus.

A complete uterine scar rupture is a rare, but potentially serious complication, for both the mother and her baby that requires immediate surgical intervention (emergency cesarean section). It is a separation through the thickness of the uterine wall at the site of a prior cesarean incision. A complete rupture refers to the separation of both the muscular part of the uterus and the serosa, the smooth outer layer that covers the uterus.

The chance that a uterine scar may separate in labor is very small.

The majority of uterine incisions are low-transverse. The scar from this type of incision is the least likely to separate in subsequent labor and birth. With this type of scar less than 5 out of 1,000 women laboring for a VBAC will be at risk for a uterine rupture.

Although the risk is small, the chances of a uterine scar separating are higher during labor than with an elective repeat cesarean.

With an elective repeat cesarean, the odds are	0.26 per 1,000
When laboring for a VBAC, the odds are	4.7 per 1,000

(Dy 2019)

Can you predict a uterine rupture?

A uterine rupture cannot be accurately predicted or diagnosed before it occurs. It can occur suddenly during labor or birth. To date, studies have shown that a uterine rupture can be detected by electronic fetal monitoring (EFM) because the women in these studies laboring for a VBAC were monitored electronically. Abnormal fetal heart tones, variable decelerations, or bradycardia (slow heart rate) have been consistently associated with uterine rupture.

Some caregivers closely monitor labor after a cesarean with a fetoscope or a hand-held ultrasound measuring device (the Doppler) in the early part of labor and use electronic fetal monitoring in active labor. Guidelines from obstetrics and gynecology professional associations recommend that women laboring for a VBAC in a hospital be offered electronic fetal monitoring.

If you labor for a VBAC with EFM you can still move around, use a birth ball, and change positions during labor while continuous electronic fetal monitoring is in use. Some hospitals have telemetry monitoring which allows people in labor to have continuous monitoring while having the freedom to walk and easily change positions. This type of monitoring uses a transmitter placed on your body to convey the baby’s heart tones to the nurses’ station via radio waves.

If the scar separates during labor, what could happen to the baby?

If the uterine scar separates, the baby may:

• Experience hypovolemia (decrease in blood volume, extreme drop in blood pressure).
• Experience an erratic heart rate.
• Be deprived of oxygen.
• Enter the peritoneum (the tissue that lines the abdominal wall and covers most of the organs in the abdomen).
• Need resuscitation.
• Need to be admitted to the ICU (intensive care unit).

What are the symptoms of a uterine rupture?

There is no single symptom that reliably confirms the separation of a uterine scar. But if the scar separates, you may experience any of the following:

• Sharp onset of pain at the site of the previous scar.
• Vaginal bleeding.
• Abdominal pain between contractions.
• A change in the pattern of your contractions.
• Low blood pressure.
• Lightheadedness, nausea, anxiety.
• Rapid heart rate.
• Chest pain.
• Unusual abdominal pain or tenderness.
• Recession of the fetal head (baby’s head moving back into the birth canal).

Experiencing a uterine rupture has serious implications for a future pregnancy.

A uterine rupture can result in scarring and damage to the uterus, which can affect future fertility and increase the risk of complications during subsequent pregnancies. A uterine rupture can cause significant bleeding, which can be difficult to control and can lead to maternal shock. If the bleeding cannot be stopped, it is sometimes necessary to remove the uterus.

Experiencing a uterine rupture has significant psychological effects. Pregnant people who experience a uterine rupture and its associated complications may experience emotional distress and trauma, which can impact their overall well-being.

What Is a window (dehiscence)?

Sometimes the uterine scar stretches thin enough to cause a dehiscence or window when the smooth outer layer is intact but the muscular layer separates. This is also known as a silent or incomplete rupture or an asymptomatic separation.

A dehiscence can be seen during a cesarean section. It occurs in about 1% to 2% of mothers with one low transverse uterine scar (side to side). It heals on its own. A dehiscence does not usually cause harm to the mother or her baby and does not require a medical response.

The risk for a uterine rupture depends on several factors:

• The number of previous cesareans.
• The type of uterine scar.
• How the uterine incision was closed (single or double closure).
• The time interval between the prior cesarean and laboring for a VBAC.
• If any induction agents were used.

The type of scar on your uterus makes a difference.

Some women have a low vertical incision on the uterus, made when there is a placenta previa (low-lying placenta), a large baby, a baby in a transverse position (lying horizontally in the pelvis), or, a premature breech delivery. Birthing people with a low vertical uterine scar can still plan a VBAC. When planning a VBAC it is important to determine if the previous low vertical scar has not stretched to the body of the uterus in the current pregnancy.

Sometimes a mother may have a “T” or “J” shaped scar on the uterus or one that resembles an inverted “T”. These scars are uncommon.

A vertical scar on the thinner and more vulnerable part of the uterus tends to separate with more intensity and results in more serious complications for mothers and babies. Birthing people who have a vertical, “T”, or “J” shaped uterine scar are at higher risk for uterine rupture.

Rarely, a mother may have a classical (vertical) scar in the upper part (the body) of the uterus. This type of incision is used for babies who are in a breech or transverse position, for women who may have a uterine malformation, for premature babies, or, in extreme circumstances when time is of the essence.

A classical scar has the highest risk for rupture.

The American College of Obstetricians and Gynecologists (ACOG), the Society of Obstetricians and Gynecologists of Canada (SOGC), and the Royal College of Obstetricians and Gynaecologists (RCOG) of Britain recommend that women with a classical uterine scar have a repeat cesarean birth.

Type of Scar and Risk of Uterine Rupture

Low transverse	4.7 per 1,000
Classical (high vertical)	4 – 9%

With a low vertical or unknown scar, there is no significant increase in rupture or dehiscence.

(Dy 2019)

The accuracy of the 4-9% rate of uterine rupture following labor after a classical scar has been questioned and may be lower than currently estimated.

How you space your pregnancy after a prior cesarean affects your risk for the separation of the uterine scar.

Risk for Separation of the Uterine Scar by Time Interval Between Births

Less than 12 months	4.8%
Less than 15 months	4.7%
Less than 18 months	1.3–7.2%
18 to 24 months	1.9%

(Dy 2019)

How your uterine incision was closed makes a difference.

During surgery, the uterine incision can be closed using a single- or double-layer closure. A single-layer closure is more likely to separate during labor than a double-layer closure.

Ripening and/or induction agents increase the odds of a uterine rupture.

Although inducing labor for pregnant people who plan a VBAC is not contraindicated, caution is recommended. The strongest factor for uterine rupture in mothers with a previous cesarean scar is the use of prostaglandins, followed by the use of oxytocin, to augment or induce labor.

Ripening and/or Induction Agent and Risk of Uterine Rupture

Oxytocin	1.1%
PGE2 (dinoprostone)	2%
PGE1 (misoprostol, Cytotec)	6%

(Dy 2019)

Ultrasound measurement of the thickness of the uterine scar is not an accurate predictor of the risk for rupture.

Care providers sometimes recommend against planning a VBAC based on ultrasound measurement of the thickness of the uterine scar.

A few studies have suggested that measuring the thickness of the scar by ultrasound may be useful in anticipating and therefore preventing a scar rupture. However, there is not enough information to prove that this method should be adopted.

Some mothers are counseled to have a repeat cesarean because their uterine scar is considered “too thin.” Obstetric associations caution that ultrasound measurement of the thickness of the uterine scar is not an accurate predictor of the risk for rupture.

Currently, there is no accurate method to assess whether or not it is safe to labor for a VBAC based on the result of ultrasound measurement of the uterine scar.

How quickly should an emergency cesarean be performed after a suspected uterine rupture?

There is no evidence performing an emergency cesarean within a certain timeline reduces short- or long-term complications for mothers or babies. However, guidelines suggest the response be as quick as possible to reduce severe maternal complications and neonatal death.

In the event of a uterine rupture, what are the outcomes for mothers and babies?

The majority of studies report that in the rare event of a uterine rupture if the labor was carefully monitored, the birth attendant was trained to attend VBAC births, and if the medical response was rapid, mothers and babies usually do well. With access to a rapid cesarean, fetal death from a uterine rupture is an extremely rare event.

Pregnant people with a prior cesarean who receive good prenatal care, whose care providers are trained and experienced with VBAC, and who labor in a facility that is equipped to provide an immediate cesarean usually have good outcomes.

With a Rapid Response to a Uterine Rupture:

Maternal mortality is	1 per 1,000 uterine ruptures
Fetal mortality is	20 per 1,000 uterine ruptures

(Togioka 2020)

Can the risk of a uterine rupture be reduced?

You are less likely to have problems with the uterine scar if:

• You go into labor on your own.
• You avoid induction with an unripe cervix.
• You avoid an induction when you had a cesarean less than 18 months prior.
• If your caregiver avoids the use of Misoprostol (Cytotec), which is contraindicated for induction for people with a prior cesarean.

The risk for a uterine rupture decreases after the first VBAC.

Research shows that the risk for uterine scar separation is lower after the first successful VBAC.

With no prior VBAC	0.87%
With 1 prior VBAC	0.45%
With 2 prior VBACs	0.38%
With 3 prior VBACs	0.54%
With 4 prior VBACs	0.52%

(Mercer 2008)

Take the time to discuss important issues with your caregiver.

During your prenatal visits, talk with your caregiver about your specific medical history and your concerns about a uterine rupture. How can these be reduced? If you are considering laboring for a VBAC and are unsure what type of uterine scar you may have, try to obtain your operative records (documentation of your surgery only).

Go over your operative record with your caregiver to see what kind of incision was made in your uterus. Find out if your uterine incision was closed with a single-layer or double-layer closure. With a single-layer closure, you may need continuous fetal monitoring during labor.

Find out what resources are available for managing emergencies that may occur with a VBAC.

Obstetric guidelines recommend that mothers labor for a VBAC in a hospital that can provide an emergency cesarean. All Level I hospitals that provide basic care for labor and birth should be able to provide an emergency cesarean, but not all hospitals have the staff and resources to do so.

If you are planning a hospital birth, ask your caregiver if the staff is specifically trained to care for women laboring for a VBAC. How would it respond in the case of a uterine rupture? How long would it take to assemble a surgical team, anesthesia, operating room staff, and pediatric care in the case of a uterine rupture? Are all members of the operating term in-house or do they need to be called in?

Are you are thinking of having your baby in a birth center or at home?

In case you or your baby need to be transferred to a hospital, your caregiver should have a plan in place and an agreement with a hospital to make sure you get the care you need as quickly as possible.

Ask your caregivers how they plan to monitor your labor and how they would respond to signs of a potential uterine rupture. How far is the nearest hospital? How long would it take to get there? Do you have a transfer agreement with the nearby hospital? Would hospital staff be immediately available in case of an emergency? Would your caregivers come with you? Would they be allowed to care for you or be with you while being cared for by the hospital staff?

A complete uterine scar rupture is a rare, but potentially serious complication, for both the mother and her baby that requires immediate surgical intervention. Less than 5 out of 1,000 women with a transverse uterine scar laboring for a VBAC will be at risk for a uterine rupture. However, the effects of a uterine rupture can be severe and life-threatening for both the pregnant person and the baby. Rapid access to a cesarean is critical to minimize complications for both.

Find out more about the benefits and risks of VBAC from Module 3 of the VBAC Education Project, What Are the Odds of a Uterine Rupture while Laboring for a VBAC?

References

Al-Zirqi, I., Daltveit, A. K., Forsén, L., Stray-Pedersen, B., & Vangen, S. (2017). Risk factors for complete uterine rupture. American Journal of Obstetrics and Gynecology, 216(2), 165. doi: 10.1016/j.ajog.2016.10.017

American College of Obstetricians and Gynecologists. (2017). Practice bulletin No. 184: Vaginal birth after cesarean delivery. Obstetrics and Gynecology, 130(5), e217–e233. https://journals.lww.com/greenjournal/Fulltext/2017/11000/Practice_Bulletin_No__184__Vaginal_Birth_After.48.aspx

American College of Obstetricians and Gynecologists. (2019). Practice bulletin No. 205: Vaginal birth after cesarean delivery. Obstetrics and Gynecology, 133(2), e110–e127. doi: 10.1097/AOG.0000000000003078

Dy, J., DeMeester, S., Lipworth, H., & Barrett, J. (2019). No. 382-Trial of labour after caesarean. Journal of Obstetrics and Gynaecology Canada, 41(7), 992–1011. doi: 10.1016/j.jogc.2018.11.008

Mercer, BM, Gilbert, S, Mark B. Landon, MB, et al. Labor Outcomes With Increasing Number of Prior Vaginal Births After Cesarean Delivery. Obstetrics & Gynecology 2008;111:285-291.
www.greenjournal.org/cgi/content/abstract/111/2/285

Togioka, B. M., & Tonismae, T. (2020). Uterine rupture. Treasure Island, FL: StatPearls. https://www.ncbi.nlm.nih.gov/books/NBK559209/

First published, September 10, 2022
Revised April 2 2023