Best Evidence: VBAC or Repeat C-Section

What is the bottom line?

• safer for you in this pregnancy
• far safer for you and your babies in any future pregnancies

KEY MESSAGES ABOUT VBAC VS. REPEAT CESAREAN SECTION:

• Scar giving way: The scar is more likely to give way during a VBAC labor than in a repeat c-section; for most women (exceptions noted below), the added risk of the scar giving way is about 4.2 in every 1,000 VBAC labors. In other words, nearly 238 women would need to experience the risks involved with repeat c-section to prevent one uterine rupture during a VBAC labor.
• Death of baby: While the scar giving way poses a threat to the baby, the added risk that the baby will die from a problem with the scar during a VBAC labor, compared with women planning repeat c-sections, is about 1.9 in every 10,000 VBAC labors. In other words, over 5,200 women would need to experience the risks involved with repeat c-sections to prevent the death of 1 baby due to uterine rupture.
• Hysterectomy in mother: If the scar gives way, some women have an urgent hysterectomy (removal of the uterus). However, cesareans also increase risk for urgent hysterectomy, and women who plan a VBAC are not more likely to experience an unplanned hysterectomy than women planning repeat c-section.
• Multiple scars in uterus: As the number of c-section scars increases, the risk for experiencing several serious problems increases for women and fetuses in future pregnancies and births. These include:
  • scar rupture in a subsequent labor
  • ectopic pregnancy: the embryo develops outside the uterus
  • placenta previa: the placenta grows over the cervix, the opening to the uterus
  • placental abruption: the placenta separates from the uterus before the baby is born
  • placenta accreta the placenta grows abnormally into or even through the uterus.
• The following factors do not increase risk of the scar giving way during labor:
  • type of uterine scar not known
  • low vertical uterine incision for prior c-section (may have been used if c-section was performed earlier in pregnancy before growth in lower part of the uterus)
  • baby estimated to be large, and to weigh more than 4,000 grams (8 pounds, 13 ounces)
  • pregnancy goes past 40 weeks, and labor is not induced
• The following factors are associated with a low risk of the scar giving way, but too few cases have been studied to know the true risk:
  • twin pregnancy: uterine rupture does not appear to be more common in twin VBAC labors compared with singleton VBAC labors
  • use of external cephalic version: turning a baby who is positioned buttocks- or feet-first (breech) to head-first position by manipulating the woman's belly does not seem to cause or be associated with uterine rupture
    
    

What problems are more common with repeat cesarean birth versus vaginal birth?

• Physical problems for mothers: Compared with vaginal birth, cesarean section increases a woman's risk for a number of physical problems. These range from less common but potentially life-threatening problems, including hemorrhage (severe bleeding), blood clots, and bowel obstruction (due to scarring and adhesions from the surgery), to much more common problems such as longer-lasting and more severe pain and infection. Even after recovery from surgery, scarring and adhesion tissue increase risk for ongoing pelvic pain and for twisted bowel.
• Hospital stays: If a woman has a c-section, she is more likely to stay in the hospital longer and to be re-hospitalized.
• Emotional well-being: A woman who has a c-section may be at greater risk for poorer overall mental health and some emotional problems. She is also more likely to rate her birth experience poorer than a woman who has had a vaginal birth.
• Mother-baby relationship: A woman who has a c-section is more likely to have less early contact with her baby and initial negative feelings about her baby.
• Breastfeeding: Recovery from surgery poses challenges for getting breastfeeding under way, and a baby who was born by c-section is less likely to be breastfed and get the benefits of breastfeeding.
• Impact on babies: Babies born by c-section are more likely to:
  • be cut during the surgery (usually minor)
  • have breathing difficulties around the time of birth
  • experience asthma in childhood and in adulthood.
• Impact on any future babies: A cesarean section in this pregnancy increases risk for babies in future pregnancies. Some research finds that babies who develop in a scarred uterus are more likely to:
  • be born too early (preterm)
  • weigh less than they should (low birth weight)
  • have a physical abnormality or injury to their brain or spinal cord
  • die before or shortly after the birth

What problems are more common with vaginal birth compared with repeat cesarean birth?

• A woman who has a vaginal birth is more likely to:
  • have a painful vaginal area in the weeks after birth
  • leak urine (urinary incontinence) (about 3 women per hundred still have a problem 1 year after birth)
  • leak gas, or more rarely, feces (bowel incontinence) (about 3 women per hundred still have a problem 1 year after birth)
• Babies born vaginally have been shown to be at higher risk for a nerve injury affecting the shoulder, arm, or hand (brachial plexus injury) (usually temporary).

What are some ways that a planned c-section may differ from an unplanned c-section?

• Best Evidence: C-Section for a summary of research comparing cesarean and vaginal birth.
• Preventing Pelvic Floor Dysfunction for in depth information about the relationship between giving birth and a woman's pelvic floor health
• details below about effects of giving birth when a woman's uterus has a scar from a previous cesarean

MORE DETAILED INFORMATION ABOUT SCAR-RELATED RISKS NOTED ABOVE

What is the added likelihood that the scar will give way (uterine rupture) during a VBAC labor?

What is the added likelihood that the baby will die as a result of the scar giving way (uterine rupture) during a VBAC labor?

What is the added likelihood of the scar giving way (uterine rupture) with any of these factors:

• type of uterine scar not known
• low vertical uterine incision at prior c-section (may have been used if c-section took place earlier in pregnancy before growth in lower part of the uterus)
• baby estimated to be large, weighing over 4,000 grams (8 lb 13 oz) or
• pregnancy extends past 40 weeks?

What is the added likelihood of the scar giving way (uterine rupture) with twin pregnancy or the use of external cephalic version (turning a baby in a buttocks- or feet-first (breech) position to a head-first position by manipulating the woman's belly)?

What is the added likelihood that a woman planning VBAC will require a hysterectomy compared with a woman planning repeat c-section?

How may a growing number of uterine scars affect future pregnancies and births?

• placenta previa: a woman whose uterus has a cesarean scar is more likely than a woman with an unscarred uterus to have a future placenta attach near or over the opening to her cervix; this increases her risk for serious bleeding, shock, blood transfusion, blood clots, planned or emergency delivery, emergency removal of her uterus (hysterectomy), placenta accreta (see next), and other complications.
  Added likelihood for a woman with a previous cesarean: MODERATE for placenta previa in a future pregnancy after having one cesarean; HIGH for placenta previa in a future pregnancy after having more than one cesarean
• placenta accreta: a woman whose uterus has a cesarean scar is more likely than a woman with an unscarred uterus to have a future placenta grow through the uterine lining and into or through the muscle of the uterus; this increases her risk for uterine rupture (see below), serious bleeding, shock, blood transfusion, emergency surgery, emergency removal of her uterus (hysterectomy), and other complications.
  Added likelihood for a woman with at least one previous cesarean: MODERATE for placenta accreta in a future pregnancy, with increasing risk as the number of previous cesareans grows
• rupture of the uterus: a woman whose uterus has a cesarean scar is more likely than a woman with an unscarred uterus to have the uterine wall give way in a future pregnancy or labor, especially at the site of the scar; this increases her risk for severe bleeding, shock, blood transfusion, blood clots, planned or emergency cesarean delivery, emergency removal of the uterus (hysterectomy), and other complications; whether a woman plans a repeat cesarean or a VBAC (vaginal birth after cesarean), she is at greater risk for a ruptured uterus than a woman with no previous cesarean.
  Added likelihood for a woman with a previous cesarean: MODERATE for rupture of the uterus, with increasing risk for two or more cesareans

References