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Old Mums and VBAC's

Offff I really do hate the Advance Maternal Age (AMA) or Geriatric Pregnancy or Older mums’ rhetoric that we see so often in the media especially when we are not old. Older than 35 is considered to be Advanced Maternal Age in the eyes of the Royal College of Obstetricians and Gynaecologists (RCOG). Some Trusts and research papers do vary on the age that they use but for this blog I will be using this age when reference AMA.


Advance Maternal Age will most likely be considered by health care professionals (HCP) as a high risk in and of itself (check out: https://evidencebasedbirth.com/advanced-maternal-age/), and then if you layer on the VBAC this will definitely put you in that high-risk tick box.


So, is it really risky to have a VBAC when you are considered AMA?


Like with all risk it is how you feel about it! Risk is something that only you can decide on, BUT it will impact the care pathway your HCP will want you to follow.

So, let’s take a look at some of the guidelines and evidence out there on AMA.

Doctor doing a routine antenatal care.
Doctor doing a routine antenatal care.

RCOG Birth after C-section Green Top Guidelines state:

“Clinicians should be aware that there is uncertainty about the safety and efficacy of planned VBAC in pregnancies complicated by post-dates, twin gestation, fetal macrosomia, antepartum stillbirth or maternal age of 40 years or more. Hence, a cautious approach is advised if VBAC is being considered in such circumstances.” Recommended best practice based on the clinical experience of the guideline development group. Not evidence-based.

And

“Factors that potentially increase the risk of uterine rupture include short inter-delivery interval (less than 12 months since last delivery), post-date pregnancy, maternal age of 40 years or more, obesity, lower prelabour Bishop score, macrosomia and decreased ultrasonographic lower segment myometrial thickness.” Evidence Level 3 (Nonanalytical studies, e.g. case reports, case series): There is not good quality evidence.

And

“Maternal age of 40 years or more is an independent risk factor for stillbirth and unsuccessful VBAC. Published advice suggests consideration of delivery of women aged 40 years or more by 39+0–40+0 weeks to reduce the risk of adverse perinatal outcomes (particularly stillbirth). However, given the likely additive effects of previous caesarean delivery and raised maternal age on the risk of stillbirth, careful consideration should be given to the timing of the delivery in women aged 40 years or above who plan VBAC. There is insufficient evidence to recommend optimum delivery timing in this subgroup of women.” Evidence level 4, Expert Opinion only. Not good quality evidence.


This is somewhat confusing. First, they state that they are unsure of the safety, then they state that it is risk factor for uterine ruptures and then goes back to insufficient evidence. I will be totally honest here there is very little evidence on the effects of AMA on VBACs especially when it comes to uterine ruptures.


The evidence or research that does keep popping up is… around the success rate of the VBACs for AMA. Not only are birthing people less likely to “attempt” a VBAC but they are more likely to have an “unsuccessful” vaginal birth.


“As women increase in age, they are less likely to attempt VBAC and more likely to have an unsuccessful labour trial.” (1)


We have to make a few assumptions here. Birthing people who are AMA are more likely to have a less supportive team because of the two contraindications (VBAC and AMA) so more likely to be persuaded to have a Repeat C-section. With those who are more likely to “try” for a VBAC, they are more likely to have interventions such as inductions, especially in the 39/40weeks (which increase the risk of a uterine rupture 0.54% - 1.91% method dependant) which are more likely to fail (up 36.5%). (3)


There are no absolute numbers (or that I can find) when it comes to the impact of Advanced Maternal Age and VBACs (specifically uterine ruptures) which begs the question is there actually an increased risk specific to vaginal births after a previous c-section?

“VBAC is a safe and feasible way of delivery for singleton pregnancy after one prior caesarean section in women with advanced age.” (2)


As always it is about balancing out the risks (your perceived risks, not the HCP’s risk). While there is very little evidence on AMA and VBACs there will be prejudices that will impact the care you receive.


Remember to use your Benefits, Risk, Alternatives, Intuition and Nothing (BRAIN) to help you make decisions that feel right for you!

 

 

 

 

(1)     Vaginal birth after caesarean delivery: does maternal age affect safety and success?

First published: 12 February 2007

(2)     Qu ZQ, Yang MH, Du MY, et al. [Outcome of vaginal birth after cesarean section in women with advanced maternal age]. Zhonghua fu Chan ke za zhi. 2017 Aug;52(8):521-525. DOI: 10.3760/cma.j.issn.0529-567x.2017.08.004. PMID: 28851168

(3)     Debelo BT, Obsi RN, Dugassa W, Negasa S. The magnitude of failed induction and associated factors among women admitted to Adama hospital medical college: A cross-sectional study. PLoS One. 2022 Jan 27;17(1):e0262256. doi: 10.1371/journal.pone.0262256. PMID: 35085270; PMCID: PMC8794164.

RCOG Birth After C-section Green top guideline - https://www.rcog.org.uk/media/kpkjwd5h/gtg_45.pdf

 



 
 
 

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