A friend of mine, who had an emergency caesarean section for her first birth, asked me recently to write about vaginal births after caesarean (VBAC). She is finding it hard to find accurate, unbiased information about the risks and benefits of vaginal birth versus elective caesarean section for subsequent births after caesareans. While I have written about this a little bit before, I thought I could just highlight a few studies that have been done, regarding VBAC.
Before sharing some relevant articles, it is important to make note that the most reliable form of research is called “randomised controlled trials” (RCT). This type of research ensures that people participating in the study are randomly assigned to one treatment or another (in this case elective caesarean vs vaginal birth), which eradicates any possible bias. Another important aspect to the RCT studies, to ensure there is no bias, is called “double blind”. This means that neither the participant nor the person collecting outcome data, knows which treatment has been assigned to which patient. Due to the nature of birth itself, neither of these methods to ensure an unbiased result are possible. Every woman is going to want to know, and moreover, choose, whether she is having a vaginal birth or caesarean. There are probably no women who would allow “the system” to allocate her to one mode of birth or another. Obviously, the people collecting outcome data would also know which type of birth each woman has had.
Does this matter? The short answer is yes. It does matter whether a study has bias either towards or against a certain treatment because the participant, or data collector’s desire for a particular outcome, can skew the results. So, each study must be scrutinised carefully to determine the extent of the bias and the accuracy of the information.
In this particular instance though, bias may actually be helpful. If a woman is biased towards having a VBAC rather than elective caesarean, this will increase her rate of success. Her passion and determination to have a VBAC will help to prepare her for the marathon of labour and birth. If a woman is biased towards elective caesarean, then obviously she will not WANT to labour, which would greatly hinder her success at giving birth vaginally.
Having said all of that, the general success of women attempting a VBAC is roughly 70% in most cases. Considering that the caesarean section rate for ALL births (including elective caesareans) is between 15-30% at most hospitals, if you are passionate about vaginal birth and have weighed up the risks, then the odds for successful VBAC are worth it.
If a woman has had a previous successful vaginal birth, either before or after the caesarean, the chance of another successful vaginal birth are increased. If the successful vaginal birth was after the caesarean, her chances are increased even further.
This study by Hoskins and Gomez (1997) discusses the success of VBAC in relation to cervical dilatation at the time the previous caesareans were performed. The study showed that the VBAC success rate was around 70% for all of the causes for previous caesareans, such as malpresentation (baby facing the wrong way eg. breech), fetal distress (baby’s heart rate too high or too low) and arrest disorders (baby getting “stuck” in the birth canal, or labour slowing or stopping) up to 9cm dilatation. The only difference was found among the previous caesareans done for arrest disorders at full dilatation, in which case the success rate was 13%. This low percentage is because if the previous caesarean was performed at full dilatation because the baby would not descend and could therefore not be pushed out, then it is reasonable to assume that subsequent babies might have the same problem, especially if the babies have the same genetic material (eg. mother and father). If the previous caesarean was done because the labour stalled or stopped, it is possible the same thing may happen is subsequent labours.
There are risks associated with VBAC that need to be considered. Uterine rupture is by far the biggest concern when considering VBAC. As you can imagine, uterine rupture is life threatening for both mum and baby. If an emergency caesarean is not performed immediately, the baby could be severely disabled or die from lack of oxygen and mum could suffer huge blood loss, require hysterectomy or die. The risk of uterine rupture however, is thankfully very low. It has been found in numerous studies to be between 0.4 – 1.5%. There is also a risk of needing to be induced for one reason or another, which among VBACs has been shown to further increase the risk of uterine rupture.
There is so much that can be written about this topic and there is an abundance of literature available to aid in informed decision making. Vaginal Birth After Caesaean section is a safe and sensible option to choose for most women desiring a normal birth following a caesarean.
Here are some useful websites…