If you've had a c-section birth, what happens next time around?

So your first baby made its entrance into the world via Caesarean section, does this mean your next birth needs to follow suit? Dr Nick Walker unpacks this increasingly common topic and helps to explain the options.

You’re pregnant again, with your second baby on the way! All the familiar feelings of the first pregnancy return, usually a bit more pronounced and sudden, but after the first trimester you’ll begin to feel a lot more ‘normal’. As you start to feel baby moving and growing, your thoughts will inevitably turn to the upcoming labour and birth. If your first baby was born by Caesarean section, there are extra considerations and important matters to address. Let’s explore these issues.

In professional maternity language, a woman who achieves vaginal birth when her first baby was born by C-section is said to have had a ‘Vaginal Birth After Caesarean’ or  a VBAC. This definition exists regardless of the circumstances of the birth, such as gestational age, reasons for vaginal or C-section birth, or even if the vaginal birth was assisted with vacuum cup or obstetric forceps. Other commonly used terminology for this concept include TOLAC (Trial Of Labour After Caesarean) and TOS (Trial Of Scar) – referring to the uterine scar created during the previous C-section being ‘trialled’ during labour.

These terms refer to the intended mode of delivery prior to labour, in contrast to the term VBAC which can only be applied after the vaginal birth has eventuated. Therefore, a woman undergoing TOLAC during the course of labour and birth, will subsequently be categorised as either VBAC or repeat C-section. These terms and outcomes are important for lots of reasons; at an individual level they help to guide advice and options for any future pregnancies and births, and they’re also used by the health system for data collation and analysis with a view to monitoring trends and therefore service planning. 

If C-section births were a rare event, the strategies and ideas around VBAC would be similarly uncommon and infrequently encountered. In reality, C-sections are the number one most commonly performed surgical procedures worldwide. In 2021, with modern healthcare systems like we have in New Zealand, nearly one in three babies are born by C-section. This figure is an overall gross statistic and only a small portion of these deliveries are related to unsuccessful VBAC however. The most relevant statistic in relation to VBAC is the number of ‘primary’ (first baby or babies, in the case of twins) C-sections. This number is still significant as 15-20% of women will deliver their first pregnancy by C-section. As the majority of women will have more than one baby, the question of attempting a VBAC will be asked for at least one in eight women!

TO VBAC OR NOT TO VBAC?

As an obstetrician, I’m often asked questions around this topic and as you can imagine, there are no black and white answers. Individual circumstances, preferences and local services available differ in every case and must be taken into account in formulating a plan for the birth. It frequently happens that, due to the uncertainties and unpredictabilities of pregnancy, plans change and then change again. Prepare to go with the flow!

Firstly, for VBAC to be considered as a goal, vaginal birth itself must be considered to be appropriate.  Regardless of the woman’s preferences, obstetric situations, such as fetal malposition (baby is not headfirst towards the cervix) and placenta praevia (where the position of the placenta blocks the cervical canal), mandate a repeat C-section. In some rare cases, the type of C-section previously done means the risks of VBAC are too high to reasonably and safely offer that as an option. In other cases, the reason for the initial C-section still exists and vaginal birth is not considered at all. In the absence of these absolutes, the decision-making gets more nuanced.

Let’s consider now declining the option of VBAC, thereby avoiding labour and birth, and planning a repeat C-section. This plan has the advantage of scheduling and certainty of outcome. Your existing child can be looked after by family support while you and a close family member (usually your partner) head into hospital where an elective C-section is performed. In general, the risks of surgery are a bit lower (only a little bit) and you have the benefit of a daytime birth with the attending midwife, surgeon, anaesthetist and theatre staff all functioning at their best. Your recovery will almost always be improved in comparison to your first C-section – women experience less post-op pain (the scar tissues are usually less sensitive than the previously unscarred tissues) and women have in-built mothercraft skills and confidence from their first baby.

This may sound pretty appealing, though the trade-offs need to be considered too – a slower and longer recovery time (now with at least two children to care for!) compared to VBAC, a longer stay in hospital (you will probably miss more early family time), and the fact that any future births will be most likely by repeat C-section. Whilst third, fourth or fifth C-sections can be performed, each one can become more difficult and prone to complication, so repeat C-sections sometimes create limits on your intended family size. Note that these are general issues, and do not take into account specific factors for every woman. 

Now let's consider going for the goal of VBAC, anticipating labour and vaginal birth. Some women have already been in labour previously, and generally their C-section was performed due to their first baby getting stressed during labour or becoming stuck in the birth canal. Some babies were even stressed AND stuck all at once! Other women have never been in labour, their first baby may have been born by pre-labour C-section due to being in breech position or the pregnancy was affected by placenta praevia.

DIFFERENCES EXPLAINED

The fundamental difference between normal vaginal birth and VBAC is the presence of a scarred cut on the wall of the uterus. This scar represents a potential weakened area of the uterus, and this weakness is put to the test under the strain of the uterine contractions that are necessary for pushing your baby into the vagina so you can then push your baby out to achieve VBAC. A problem occurs when the scar becomes stretched to the point of muscular layer separation (called dehiscence by health professionals) or to the point of total rupture of the uterine wall. This is extremely unlikely to happen without labour, though it has been reported in the medical literature from time to time. So the major danger, or risk, occurs during labour.

Clues to uterine scar dehiscence or rupture can be observed during labour, and your LMC caring for you will be alert to any symptoms or signs of impending trouble. It is strongly advised that your labour happens in hospital, where the ability to manage uterine scar problems can occur safely and without delay. Uterine scar dehiscence disrupts the muscle connections and therefore the contractions cannot function properly and vaginal birth will not happen, however the baby will be okay. Complete uterine rupture is very serious, as not only is vaginal birth impossible but also the baby can be pushed through into your abdominal cavity leading to the need for extremely urgent abdominal surgery to birth safely. Fortunately this is a very rare occurrence, occuring in one in several hundred women attempting VBAC.

MAKING THE DECISION

For most women considering trying for a VBAC, the balance of the decision can be swung by comparing the very small odds of a negative outcome versus a relatively good chance of a successful vaginal birth. Depending on the circumstances of the previous C-section, successful VBAC will occur between 50% and 90% of the time. This wide range of success can be attributed to a lot of things, and there are clinical calculating tools available which can generate a probability of success given known factors which are inputs to the equation. Factors favouring successful VBAC (and their opposites) include spontaneous (versus induced) labour, small or medium (versus large) fetal size, younger maternal age and lower body weight.

Women who have previously had a vaginal birth (including VBAC) have an especially high VBAC rate. Women who previously underwent a C-section with a baby of medium size which got stuck in labour usually do not VBAC so successfully, as they may have a smaller pelvic capacity which limits the ease of vaginal birth. Women who had breech babies or underwent pre-labour C-sections for other reasons have essentially untested pelvic adequacy and have intermediate rates of successful VBAC. It is important that these things are taken into account during decision making.

Having made provisional plans and preferences, you can get on with preparing for your new baby’s arrival. Be reassured and confident, and always remember that the baby will arrive no matter what the process, and certainly prioritise keeping time and energy free to account for the new addition to the household above the eventual mode of delivery ... VBAC or otherwise!

Dr Nick Walker is a specialist obstetrician working in public practice at National Women's Hospital and private practice in Auckland. He divides his time between these roles and helping his wife care for their four children.