Let's "Rupture" the myths surrounding Vbac
This week I got a message from someone seeking guidance on VBAC, and this was her text:
“They were saying that if it’s within 2 years of my last [CS] then my chances of my scar tearing and me and baby both not surviving were high.”
And because I am me, I had to make an IG post and blog and email to disseminate TRUTH so that women can learn to advise each other with evidence and sound advice.
What is a uterine rupture anyways?
This is when your previous Caesarean scar opens while in labour with a subsequent baby, and this wound in the uterus leads to a disruption of blood flow to baby. If not treated by quick delivery of the baby and repair of the tear, it can lead to death for mom or baby.
Let’s clarify some terms you’ll see associated with aiming for a vaginal birth after having had a prior CS:
Vaginal Birth After Caesarean
Trial Of Labour After Caesarean
(I am not a fan of this patronizing and condescending term, so you’ll see me continue to use more empowering terms)
Elective Repeat Caesarean Section
In general, 60-80% of women who labour and desire a vaginal birth after a prior CS will end up with a vaginal birth, which means that 20-40% of women will end up with another CS for one reason or another.
In Ontario midwifery, 75% of women who attempt a VBAC will be successful.
With such high success rates, it is unfortunate that the Canadian rate of women who aim for a VBAC is only 30% whereas Ontario midwives have double the rate at 61%.
If your goal is a VBAC, your success rate will be higher and more supported if you choose a midwife to care for you.
What do Canadian guidelines say about VBAC?
Society of Obstetricians and Gynaecologists of Canada 2019 Trial of Labour After Caesarean Clinical Practice Guideline:
“Provided there are no contraindications, a trial of labour after Caesarean should be offered to all women with 1 previous low-segment transverse Caesarean section after appropriate discussion and documentation of maternal and perinatal risks and benefits. The discussion should be documented.
Association of Ontario Midwives 2021 VBAC Clinical Practice Guideline:
“Midwives should recommend planned VBAC to clients who have had one previous CS. Informed choice discussion should include [risks, benefits, etc.] This discussion, including the client’s decision, should be documented in their chart.”
TOLAC is supported by all governing bodies globally as an appropriate way to reduce overall CS rates.
That said, can you see which guideline above is more supportive of what can be an incredibly redemptive process, especially for women who have previous birth trauma??
Because I’m a little lazy, here’s a screenshot of my online ‘Prenatal Education for a Fulfilling Birth’ ecourse outlining the NUMEROUS benefits of a successful VBAC compared to the main risk that every fear mongering care provider will throw in your face: Uterine Rupture.
Let's dig into the data on Uterine Rupture!
Let’s first discuss the difference between Relative Risk and Absolute Risk so you can understand statistics and data better.
Relative risk (RR): your risk relative to or compared to another group (usually the control group in a study)
Absolute risk: the actual risk for YOU
When making decisions, request that evidence and statistics be given in the form of ABSOLUTE risk.
According to the AOM VBAC Clinical Practice Guideline quoted above, there are only 10 observational studies between 1994-2020 that provide good data on VBAC versus ERCS.
In these 10 studies:
- There was no difference in maternal mortality,
- The uterine rupture relative risk is 4.3 but the absolute risk is still low (1/200). This means that women who labour are 4.3 times more likely to have a rupture than those who plan a repeat CS but their own risk is still about 0.5%.
Do you see why it’s SO important to ask for Absolute Risk? Relative Risk is often used as a fear tactic.
The AOM document goes on to say for women who VBAC:
- 22 more women per 1000 will have an intrapartum (in labour) infection (which makes sense since they actually HAVE an intrapartum compared to women who opt for a scheduled CS (RR 1.59),
- 1 more per 1000 neonates will die (RR 2.61),
- 5 more per 1000 neonates will acquire infection (which makes sense if more moms gets an infection in labour, RR 1.40),
- 9 more per 1000 will have an Apgar score less than 7 at 5 mins, meaning they are still needing breathing support (RR 2.93).
So what if you've had 2 or more Caesareans?
Here’s what the AOM Guidelines states for women who VBAC after 2 Caesareans (you may see the term VBA2C to denote this):
- Maternal mortality: no difference,
- Perinatal death rate essentially the same (RR 1.37),
- 2 more women per 1000 will experience a uterine rupture (RR is 8.67 which sounds way more scary when said that way)
- 3 fewer per 1000 will undergo a Hysterectomy (RR 0.52)
How much time should pass after your CS before a VBAC is encouraged?
The likelihood of uterine rupture (after looking at over 79 000 participants in 4 studies) suggests a delivery interval of less than 24 months results in a relative risk of almost two times the risk of uterine rupture, or a 1/100 or 1% absolute risk, although the chance of VBAC is actually higher!
It’s important to recognize that we all view “risk” differently, and we have different thresholds for risk. Some may say 1/200 is low and within their comfort zone, but 1/100 is “too risky”, while others will look at that and say “but there’s still a 99% chance I WON’T rupture and that’s a high probability for me”.
So what factors affect VBAC success rates?
Next week I’ll present the evidence regarding VBAC at home, so stay tuned!!
Let me know how you feel about all this information! Head on over to my Instagram page and comment on my March 1 post on VBAC! I would love to hear where you land on what is too risky for you!
Want more info?
- Evidence Based Birth Podcast 113: The Evidence on VBAC”. 28 January 2020. Podcast transcript found here.
- “Deciding how to give birth after a Caesarean”, Association of Ontario Midwives client handout found here
- “Power to Push Campaign”, 2010, BC Women’s Hospital + Health Centre Information Booklet found here
Association of Ontario Midwives. Vaginal Birth after Previous Low-Segment Caesarean Section. 2021; Clinical Practice Guideline No. 14.
Dekker, R. “EBB 113: The Evidence on VBAC”. 28 January 2020. Podcast transcript. Evidence Based Birth. Accessed 18 March 2021.
Dy, J., DeMeester, S., Lipworth, H., Barrett, J. “No. 382-Trial of Labour After Caesarean”. 1 July 2019. Journal of Obstetrics and Gynaecology. Volume 41, Issue 7, P992-1011.