A complete uterine scar rupture is a potentially life threatening condition for both the mother and/or the baby that requires immediate surgical intervention. It is a tear through the thickness of the uterine wall at the site of a prior cesarean incision. The majority of cesarean uterine incisions are low-transverse. The scar from this type of incision is the least likely to rupture in a subsequent pregnancy, labor, and birth.

Scar tissue in the uterus will expand and stretch as the uterus grows during pregnancy. Sometimes the scar stretches thin enough to cause a dehiscence or window. This is also known as a silent or incomplete rupture or an asymptomatic separation. A dehiscence can be seen when women have a scheduled repeat cesarean or after delivery when women had a VBAC. They occur in about 1% to 2% of mothers with one low transverse scar (side to side). They heal on their own and do not need medical treatment.

How often does a cesarean scar rupture occur?

Fortunately, uterine ruptures from a prior cesarean with a low-transverse scar is a rare event and occurs in less than 1% of women laboring for a VBAC. The risk for uterine rupture is approximately 0.3% to 0.7% for women laboring for a VBAC compared to 0.022% to 0.026% for women who have an elective repeat cesarean.

Uterine ruptures have also been known to occur in some women who have never had a cesarean. This type of rupture can be caused by weak uterine muscles after several pregnancies, excessive use of labor inducing agents, a prior surgical procedure on the uterus, or mid-pelvic use of forceps.

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. Women 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 woman may have a "T" or "J" shaped scar on the uterus or one that resembles an inverted "T". These scars are very rare. Rarely, a woman 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 vertical scar on the thinner and more vulnerable part of the uterus tends to rupture with more intensity and result in more serious complications for mothers and babies. Mothers who have a vertical, “T”, or “J” shaped uterine scar are at higher risk for uterine 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 scar have a repeat cesarean birth.

What are the symptoms of a uterine rupture?

A uterine rupture cannot be accurately predicted or diagnosed before it actually occurs. It can occur suddenly during labor or delivery. A few studies have suggested that measuring the thickness of the scar by ultrasound or following closely the pattern of contractions in labor may be useful in anticipating and therefore preventing a scar rupture. However, there is not enough information to prove that these methods should be widely adopted.

Several symptoms have been identified, but do not necessarily occur with every uterine rupture. Signs of uterine rupture that may or may not be present.

• Vaginal bleeding
  
  
• Sharp pain between contractions
  
  
• Contractions that slow down or become less intense
  
  
• Abdominal pain or tenderness
  
  
• Recession of the fetal head (baby's head moving back up into the birth canal)
  
  
• Bulging under the pubic bone (baby's head has protruded outside of the uterine scar)
  
  
• Sharp onset of pain at the site of the previous scar
  
  
• Uterine atony (loss of uterine muscle tone)
  
  
• Non-reassuring fetal heart tones (fetal distress)

Abnormal fetal heart tones, variable decelerations, or bradycardia (slow heart rate) have been consistently associated with uterine rupture. It is important to note that with a uterine rupture, labor sometimes continues, there is no loss of uterine tone or amplitude of contractions.

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. Although some caregivers closely monitor VBAC labors with a fetoscope or a hand-held ultrasound measuring device (the Doppler), no VBAC studies have yet been published on this method. Guidelines from the ACOG, SOGC, and RCOG recommend that women laboring for a VBAC be offered electronic fetal monitoring.  

How does the risk of a rupture compare with any other complications of labor whether the mother had a prior cesarean birth or not?

For women whose labors begin spontaneously, uterine rupture is reported to be less than 1% and the risks similar to or less than the risk of any other unpredictable complication of labor and delivery.

Medical experts state that the risk of a uterine rupture with one prior low-horizontal incision is not higher than any other unforeseen complication that can occur in labor such as fetal distress, maternal hemorrhage from a premature separation of the placenta or a prolapsed umbilical cord.

Respected researchers have concluded that the probability of any woman in labor needing to have an emergency cesarean compared to other unforeseen complications is approximately 2.7% or up to 30 times as high as the risk of uterine rupture.

What happens if the scar ruptures?

Although uterine scar ruptures for women laboring for a VBAC are rare, the medical response is a rapid cesarean.

The longer it takes to diagnose and respond to a uterine rupture the more likely it is that the baby and/or the placenta can be pushed through the uterine wall and into the mother's abdominal cavity putting women at increased risk for hemorrhage and babies at increased risk for neurological complications and very rarely, death.

The authors of A Guide to Pregnancy and Childbirth, an internationally respected evidence-based text, state that any birthing facility equipped to respond to a medical emergency can care for women laboring for a VBAC.

Whereas ACOG guidelines for an emergency cesarean previously allowed for a maximum response time of 30 minutes for an obstetric emergency, current VBAC guidelines issued by ACOG recommend that birth facilities who care for women laboring for a VBAC should have a physician capable of performing an emergency cesarean, anesthesia services, and staff "immediately available." The National Institutes of Health (NIH) Consensus Development Statement on VBAC (March 2010) indicated that there is no scientific evidence to support this recommendation. The American Academy of Family Physicians guidelines for a trial of labor after a cesarean (TOLAC) state that VBAC should not be restricted only to facilities with available surgical teams present throughout labor since there is no evidence that these additional resources result in improved outcomes

Birthing facilities vary in their guidelines and protocols for VBAC and response time to a uterine rupture and other unforeseen complications of labor. Many US facilities have recently determined that they don't have the capability to respond "immediately" in case of uterine scar rupture. The NIH reported that this recommendation influenced many hospitals and providers to stop providing medical care for VBACs.

The International Cesarean Awareness Network (ICAN) compiled a directory of U.S. hospitals that do and do not provide medical care for VBAC. Women can access ICAN’s Hospital VBAC Data Base at http://ican-online.org/vbac-ban-info.

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.

The Vermont/New Hampshire VBAC Project findings show the overall risk of infant death from a VBAC attempt is 6 per 10,000 compared to 3 per 10,000 planned cesarean births.

Women 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 immediate medical care usually have good outcomes. To date there have been no reports of maternal deaths due to uterine rupture. According to the National Institutes of Health Consensus Development Report on VBAC , while rare for both, laboring for a VBAC and elective repeat cesarean, current research shows that maternal mortality is significantly increased for elective repeat cesarean, 13.4 per 100,000, compared to 3.8 per 100,000 when laboring for a VBAC.

Can the risk for a uterine rupture be reduced?

Although it is not possible to predict which women are likely to experience a uterine rupture while laboring for a VBAC, recent studies suggest that the risk for uterine rupture is somewhat higher when:

• Labor is induced. Misoprostol, a drug intended to treat gastric ulcers, is associated with a high risk of uterine rupture and should not be used to induce labor for women who plan VBAC.

• The prior cesarean incision was closed with a single-layer of sutures (single-layer closure- often done in recent years to shorten the time in the operating room) as opposed to two layers of sutures (double-layer closure).

• Women become pregnant and labor for a VBAC within less than 18 to 24 months after a prior cesarean.

• Women are older than 30 years of age.

• Maternal fever was a consequence of a prior cesarean birth.

• A classical uterine incision was used in a prior cesarean birth.

• Women had two or more prior cesarean births.

• Women labor for a VBAC after the 40th week of pregnancy

Informed Choice-Informed Refusal

Current US health law and medical-ethical guidelines give childbearing women who once gave birth by cesarean the option of laboring for a VBAC or scheduling an elective repeat cesarean. ACOG’s current guidelines for VBAC state that women with one prior cesarean should be counseled about VBAC early during pregnancy and offered a trial of labor. Physicians should give women comprehensive information about the benefits and risks of VBAC and elective repeat cesarean, but ultimately the decision should be made by the patient.

For additional information see:

American Academy of Family Physicians. Trial of Labor After Cesarean, Shared Patient-Physician Decision Tool
www.aafp.org/online/en/home/clinical/patiented/counselingtools/tolac.html

Childbirth Connection. Should I Choose VBAC or Repeat Cesarean?
childbirthconnection.org/article.asp?ClickedLink=293&ck=10212&area=27

Childbirth Connection. VBAC and Cesarean Birth: How Do the Risks Compare?

Northern New England Perinatal Quality Improvement Network, Vermont/New Hampshire VBAC Project. Birth Choices After Cesarean. (PDF)

References:

American Academy of Family Physicians. Trial of Labor After Cesarean
www.aafp.org/online/en/home/clinical/clinicalrecs/tolac.html

American College of Obstetricians and Gynecologists. Practice Bulletin Number 115, Vaginal Birth After Previous Cesarean, August 2010.
journals.lww.com/greenjournal/Citation/2010/08000/Practice_Bulletin_No__115__Vaginal_Birth_After.40.aspx

Enkin et al 2000.
www.vbac.com/chapter38.html

Flamm, B. and E.J. Quilligan, Editors. Cesarean Section Guidelines: Appropriate Utilization. Elsevier, 1995.

National Institutes of Health Consensus Development Conference on Vaginal Birth After Cesarean: New Insights.
consensus.nih.gov/2010/vbac.htm

Northern New England Perinatal Quality Improvement Network, Vermont/New Hampshire VBAC Project.
www.nnepqin.org/site/page/vbac