VBAC (Vaginal Birth After Cesarean): An Intro

In this country, 9 in 10 women with a history of cesarean will go on to have a repeat cesarean delivery in any future pregnancy.

Only 1 in 10 will have a vaginal birth after cesarean, known colloquially as “VBAC”. 

When this statistic is reported, it is often without the necessary context; people may understandably conclude that if 9 in 10 women with a history of prior cesarean have cesareans in subsequent pregnancies, it is because VBAC is very difficult to achieve, or so dangerous that nobody in their right mind would plan for one.   In reality, the truth is much more complex.

These statistics have more to do with the politics of medicine and women’s reproductive rights than they do with safety, or with likelihood of VBAC “success”.

The most publicized risk of VBAC is a small (less than 1%) chance of a potentially dangerous complication called uterine rupture.  Uterine rupture involves the uterus tearing open, usually during labor.   This can occur along the old cesarean scar, or in areas of the uterus that are unscarred, such as the posterior uterine wall or down near the cervix.  In such case, the baby may be at risk of death or serious injury, and the mother may be at risk of hemorrhage, shock and hysterectomy.

Though serious, the risk of a uterine rupture is as small or smaller than the chances of other emergencies inherent in all vaginal births (such as cord prolapse, shoulder dystocia and placental abruption).  The required management is an emergency cesarean, which all hospitals offering maternity services can perform.  Read more here.

Repeat cesareans also present real risk to the mother — in particular, life-threatening abnormal placental attachment in future pregnancies.  Between this and the fact that uterine rupture is rare, the American Congress of Obstetricians and Gynecologists (ACOG) considers VBAC to be a safe and reasonable choice for most women with one or two prior cesareans, and an important means of reducing preventable morbidity and mortality from overuse of cesarean surgery.

ACOG’s guidelines also make clear that most women who plan a VBAC will be successful, and that even women who are not considered good “candidates” for a VBAC are still entitled to refuse surgery in favor of laboring.  Most “unsuccessful” VBACs end in a non-emergent repeat cesarean for non-progressive labor — not a uterine rupture or other emergency.

Despite this, the rate of VBAC remains low because physicians and hospitals often prefer and recommend cesarean delivery, or even outright ban VBACs, for reasons of risk management and convenience.  In other words, fear of being sued for a uterine rupture, and the perception among physicians that cesarean sections conveniently eliminate this liability, drive the high rate of repeat cesarean delivery and low rate of VBAC.  This is fascinating, because electing for a repeat cesarean does not eliminate risk.  It merely trades risk to the baby in this delivery, for risk to the mother — not only in the present delivery in the form of increased risk of infection and other surgical/wound complications, but in the next delivery (in the form of potential for placenta accreta).

Placenta accreta is when the placenta in a subsequent pregnancy grows too deeply into the uterine lining — usually at the site of the prior cesarean scar.  This can cause life-threatening hemorrhage following birth when providers attempt to remove the placenta from the uterus.  Read more about placenta accreta as a downstream consequence of repeat cesarean here.

Unfortunately, when recommending repeat surgery to women with a history of cesarean, obstetricians rarely, if at all, disclose the risk of placenta accreta in future pregnancies.  The ethics and legalities of this are extremely concerning: accreta now occurs in as many as 1 in 272 pregnancies and is widely considered to carry a maternal death rate of about 7% (1 in 14).  

This is especially striking when you consider that the denominator of the 1 in 272 statistic is ALL PREGNANCIES, not just those over a prior uterine scar.  In other words, the uterine rupture statistic (approximately 1 in 200 depending on the study) is limited to those with a prior cesarean scar –meaning the incidence is less common than a statistic of 1 in EVERY 272 pregnancies, history of cesarean or not.

So placenta accreta may, at this point, be more common and more deadly than uterine rupture, yet obstetricians are still far more likely to recommend repeat cesarean section (RCS) than VBAC.  While some may argue that is because they are only obligated to maximize the odds of a positive outcome for the mother/baby dyad in front of them, rather than thinking ahead to a hypothetical future pregnancy that does not yet (and may never) exist, it is important to understand two things: (1) even if a parent decides they do not want any more children, half of all pregnancies in this country are unplanned.  And some folks change their mind, especially if their family situation changes (for example, re-marrying at a later date).  (2) physicians have a legal and ethical duty to facilitate informed consent when recommending medical interventions like cesarean delivery.  Informed consent requires disclosing those risks that are significant enough to be material to a reasonable patient’s decision.  This means that obstetricians are obligated to disclose to disclose the risk of placenta accreta in a future pregnancy, and the associated maternal mortality rate, when consenting women to cesarean delivery (whether repeat or primary).  The fact that they are not is a serious failure in law and ethics.

So what does all this mean?  It means that if you are pregnant after a cesarean, fear, politics, risk management and physician preference may filter the options and information available to you in navigating your care.

It can be really difficult to make decisions in the midst of all this noise and pressure.  Please stay tuned for my next blog post, which will feature tips for planning a VBAC.