VBAC - A Closer Look - Kamm McKenzie OBGYN

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VBAC – A Closer Look

Originally written and published by Dr. Bernstien in February of 2016.

VBAC is an often desired delivery for patients who are seen at Kamm McKenzie.  In fact, we have many women who chose to come to us, or transfer their care to us mid-pregnancy, because of our willingness to support a woman’s decision for VBAC and our success rates of vaginal birth.  I think it is important for all to know that we take VBAC seriously and want our patients to be educated on the risk and benefits of this.  There is an excellent, concise article on VBAC on our website already that can be viewed here.

Let’s start by clarifying some terminology.  VBAC stands for vaginal birth after cesarean.  TOLAC stands for trial of labor after cesarean.  Many times these are used interchangeably, but I wanted you to know what they stand for in case you see these terms on other websites.  I am going to use VBAC since that seems to be the more common term amongst my patients.  

Maternal Risks:

  • Uterine rupture is when the incision in the inside, on your uterus, opens during labor.  This happens approximately 1% of the time when women attempt VBAC.  It can lead to serious maternal and neonatal complications.  While not impossible, uterine rupture is unlikely for a repeat c-section.
  • Infection rates are similar between VBAC and repeat c-section.  For VBAC, the infection is usually chorioamnionitis (infection in the bag of water) that, if detected, requires maternal antibiotics in labor and then antibiotics for the baby post birth.  For repeat c-section, there are higher risks of postpartum pelvic infections, which makes sense because there was surgery.  
  • Hemorrhage rates, and blood transfusion rates, are similar between VBAC and repeat c-section.
  • Maternal Death is fortunately VERY rare for either category; however, it is actually higher for repeat c-section than VBAC.
  • Deep vein thrombosis (DVT) happens at similar rates with VBAC and repeat c-section.

*** It is of the utmost importance to know that the above maternal risks are higher if the VBAC fails thus requiring a repeat c-section.  There would be a higher risk of infection post operatively, hemorrhage and blood transfusions during or after the surgery, hysterectomy due to hemorrhage or uterine rupture, and maternal death.***

Maternal Benefits:

  • A scheduled delivery, usually via repeat c-section, is obviously more convenient.  I WOULD NEVER recommend mode of delivery based on convenience… let’s be honest, that is pretty silly.  While inductions of labor can be scheduled for VBAC, it is important to know that one of the best indicators of successful VBAC is spontaneous labor.
  • Length of hospitalization is shorter with successful VBAC.  There are fewer postpartum complications and a quicker return to normal function.  This is one of the bigger points for many women, especially those with young, dependent children.
  • If you know you are on your last pregnancy and are 100% sure you want permanent sterilization, then this is readily accomplished during a c-section.  That being said, there are MANY contraception options available after vaginal birth, so I would only consider the option of sterilization as a small benefit of repeat c-section.

Perinatal Risks (ie risks to the baby before and after birth):

  • Death of the baby in utero or shortly after birth is higher for VBAC than repeat c-section.  That being said, the absolute risk is very low, at around 1/1000.
  • Brain injury (due to lack of oxygen) to the baby is also higher for VBAC than repeat c-section.  Again, the absolute risk is very low, at around 1/1000 for VBAC and even lower with ERCD.
  • Respiratory issues are slightly higher with repeat c-section than VBAC.  This is because there are known pulmonary benefits to a baby when it traverses the birth canal.  
  • Infection in the baby is a little higher with VBAC vs repeat c-section (5 vs 2%).

*** There are no significant changes in the 5 minute APGAR score between VBAC and repeat c-section.***

So there you have it, all the scary stuff that I, as your OB provider, have to let you know about. But let’s simplify the complications to a couple of important numbers.  VBAC is associated with a 1% risk of uterine rupture, and if this happens there is a 1 in 10 chance of a catastrophic event to you or your baby (brain injury or death).  Thus there is an overall rate of SERIOUS complication of 1/1000.  If you choose to attempt VBAC, when you arrive at the hospital, the nurses will have you sign a consent stating you understand these risks.

Now, let’s try to hammer out what to me is the most important aspect of this conversation… WHO should really try this and who should not?!?

Optimal candidates have had only ONE prior low transverse cesarean section. (This is the normal kind of c-section and used 99% of the time.  We do like to review operative reports of prior c-sections to make sure someone is a good candidate.)  For these women the success rates of a VBAC are reported between 60-70% for most.  There are factors that influence the likelihood of success as outlined below.  These are all very much common sense but let’s review them.

  • If you have ever had a successful vaginal delivery (before or after your c-section) then your VBAC success rate is MUCH higher.
  • If you present to the hospital in active labor, are at or before your due date, and have what is presumed to be a normal sized baby, then your VBAC success rate is higher.  Most studies use 4000g as a good cut-off for success rate.  This is about 8lb 12oz.  It is so hard to predict estimated fetal weight when pregnant; however, if your last baby weighed 9+ pounds this one will likely be there too!
  • If your prior c-section was for malpresentation (breech, etc) or for another reason not likely to recur (such as placenta previa or the fetal heartbeat was non-reassuring) then you VBAC success rate is higher.  IF, however, your c-section was for labor that stalled out or the inability to push the baby out, this markedly decreases your VBAC success rate.  Some estimate an average of 54% success in these cases.
  • Some maternal demographics also affect success rates.  Obesity decreases success.  Taller women have a higher success rate.  Non-Hispanic white women have a higher success rate than Hispanic, African American, or Asian women.  
  • Getting pregnant within 6 months of your prior c-section decreases VBAC success rate because the uterine rupture rate is a little higher.
  • Lastly, and probably a reason many of you may choose Kamm McKenzie, delivery at a private teaching hospital, such as WakeMed Raleigh on New Bern Ave, gives you the highest VBAC success rate when compared to other facilities.  I think that just comes with comfort by all involved including nursing, doctors, and support staff.

The last thing I want to mention is induction of labor.  As mentioned above, spontaneous labor prior to 40 weeks increases VBAC success.  However, many times this does not happen.  Some women choose to schedule repeat c-section on or around their due date and, if they were to achieve active labor spontaneously, proceed with attempted VBAC.  Others want to try VBAC regardless.  Induction of labor almost always requires pitocin and we know this increases uterine rupture rate.  The American College of OBGYN still supports pitocin use in women with a prior cesarean section.  

In summary, it is the decision of the patient to choose what she wants with regards to mode of delivery.  We can only guide you based on medical data and our personal experiences.  We are happy to help you with your goals as long as you understand and acknowledge risks are present for both VBAC and repeat c-section.   Lastly, it is impossible to predict who will have a successful VBAC and who will not.  We can only guide you based on the data presented here.

Regardless of what you choose, we are here to support you and thank you for choosing to have your baby with Kamm McKenzie OBGYN.

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