A Love Affair with VBAC Stats

At some point during a VBAC journey, it is likely you will start a love affair with stats. I know, because I’ve been there. I’ve courted stats, I’ve had lover’s tiffs with stats and, I’m pretty sure, I’ve even taken them to bed.

So, here follows a lengthy discussion which – if you choose to read it – may mean you won’t be able to read another VBAC success stat again without picturing a dancer on a pole. (And yes, you can thank me later.)

The Love Story Begins

While you’re waiting for the retails stores to have crystal balls on special, having facts and figures upon which to base your decisions is the next best thing, right? And, who doesn’t love a sexy stat or two, especially when they tell you what you want to hear.

In fact, I think stats can do even more – with the right stats, you might gain some credibility in your discussions with a care provider, for example. Stats might even lead you to make a critical choice which is the difference between the birth outcome you desire and the alternative. And, in this day and age, we plebs have even more stats at our fingertips than ever before – this is perhaps our greatest time of empowerment. Repeat after me: COLLECT ALL THE STATS!

But, stats – like all forms of information (and indeed all new relationships) – need to be approached with certain level of caution. Like any meticulously constructed Instagram account, the best looking stats have possibly been cropped and filtered to create a certain outcome. And, like that Instagram pic which crops out your ‘shagbuster’ trackies, stats only tell you part of the story you want – it is your job to gather the rest of information you need to give these numbers *context*. (Because, let’s face it, everyone secretly only wants to see the stuff that is cropped *out* of Instagram pics, right?)

Let’s take a popular general statistic like ‘women have a 75% chance of VBAC success’. This might fill you with confidence for your planned VBAC. Indeed, it *should* give you confidence in your decision to plan a VBAC, because it sounds pretty darn good. Crikey, if I were told I had a 75% chance of winning lotto, I’d be actually getting dressed today (and that’s saying something!) and heading out to my local newsagent to buy myself a ticket.

However, here’s the catch: this statistic is the promise of an outcome, not a guarantee. (Darn it – I might have just gotten dressed a little prematurely! Never mind – Instagram will help me to crop my shagbusters out.)

And, here’s a harsh fact: Not all women have an equal 75% chance of successful VBAC, just like not every punter has an equal chance of winning lotto. This is an average, a OSFA number. It is a handy number to know, but it is not necessarily your Magic Number. We logically know that my chance of winning lotto goes up and down depending on which numbers I choose (if i do indeed choose my own numbers), and how many tickets I buy. In a similar way, some women are more likely to VBAC than others.

Harsh Fact #2: The effect of your choices on your Magic Number is really only ever known retrospectively. This is the awful truth about stats – sometimes they’re all talk. But, sometimes they turn out better than you thought.

So, while you’re in the thick of it and don’t yet have the benefit of hindsight, let’s at least try and make this stat work a little better for you. And, how do you do that? You need to work it, baby! Think of yourself as the RuPaul of the VBAC Stat World! You need to go forth like the fierce mama you are and get more information to frame this number within your own context (feel free to leave the killer heels and spandex to RuPaul, however – I much prefer ugg boots and jeans!). Don’t leave this stat standing there, naked, shivering and pleading for a coat – dress it up in the important stuff, like ‘who is my care provider?’ and ‘where am I birthing my baby?’

As you start adding details to the 75% stat, watch your Magic Number bounce up and down. Truthfully, I have a dance pole in mind here with this… And now so do you. (I did warn you!).

Think of 75% as the sweet zone on the pole. When you jump on, you might be a bit rusty and find yourself at about 45%. That’s okay – the beauty about VBAC is that you have at least nine months to do something about that. So, you start researching, making choices and asking questions. This is you climbing a little higher. You go back to your obstetrician and hear that they have an 80% VBAC rate. You beauty! You climb higher. But, after reading about the difference between VBAC rates and success rates, you ask your obstetrician how many VBACers they oversee – their answer is five in the past year. Uh oh, your Magic Number just slipped a little. You then get to your 36 week review and your care provider starts mentioning ‘big baby’, ‘small baby’, ‘low amniotic fluid levels’, ‘high amniotic fluid levels’, ‘due dates’, ‘going over’… Yikes, suddenly you feel like you’re at risk of face-planting on the tacky floorboards beneath you. (Actually, so is the landlord – they’re stepping in to stop the show lest it becomes a public liability claim.) (And yes, this landlord is a metaphor for a ‘bait and switch‘ care provider – they do exist.) So, you quickly change tack, get a second opinion or two and make some new decisions… Phew! You might have just avoided a repeat Caesarean (and an insurance claim).

You see, the VBAC success rate is not guaranteed until *after you give birth* (and you jump down from the dance pole). This is actually good news!

Don’t think of a VBAC success stat as a static number – it is a fluid thing. The birth choices you make, the preparation you do, and the support you have around you all shift this number up and down. Stats are great to help you understand what are reasonable expectations – they help you to make the best decisions possible when the crystal ball you bought online from China is caught up in the Australia Post Christmas rush. But, at the end of the day, stats are numbers which can be sliced and diced numerous ways for various agendas – like any good relationship, it is important to remember that you have control over what you bring into the picture, too.

Digesting VBAC Stats: Know What You’re Eating

Chocolate by André Karwath aka Aka – Own work. Licensed under CC BY-SA 2.5 via Wikimedia Commons – httpcommons.wikimedia.orgwikiFileChocolate.jpg#mediaviewerFileChocolate.jpg

If you’re a South Australian mother researching VBAC, chances are that you’ve stumbled across the Pregnancy Outcome Unit’s ‘Pregnancy Outcome in South Australia’ reports. (If you haven’t already, you just did.) Seriously, if you love stats which are actually *relevant to a local context*, these publications are to the World of VBAC Stats what Pana chocolate is to the world of cocoa-based confectionery. (And, if you haven’t yet stumbled across Pana chocolate, make sure you do – it will help you stay up late reading stats.)

Whet your appetite!

Now, these documents are really a bit of a beast. There is so much information in them that they are best consumed piece by piece (a bit like Pana chocolate). It pays to pace yourself – take notes, highlight things, digest them. Come back in the morning with fresh eyes and re-read them again. Take more notes and eat more chocolate.

One of the tastiest pieces of information for a VBACer is found under ‘Clinical and Maternity Performance Indicator: Vaginal Birth following Caesarean Section’ (shortened to ‘VBAC’ when ‘VBFC’ would actually be correct in this case… I guess it makes it sound like VBACers have their own footy club, though). This is where you will find the magical number which answers the question: ‘How many women VBAC in SA?’

Let’s hold that thought – how far through that block of Pana are you right now? Is it still tasting sweet? Is it melting in your mouth and slipping down your throat like a silken river caressing your insides? Well, enjoy that, because what I’m about to say will leave a bitter taste in your mouth.

For years, the VBAC rate in South Australia has consistently been at about 17%. (And, if you’re playing from interstate, the national rate is usually around 16% – you can track this in the Australian Mothers and Babies reports.)

I can hear you suddenly choking on your chocolate. What?! Did I read that correctly?! Only 17% of VBACers actually VBAC? And, because you’ve read them: Don’t the South Australian Perinatal Practice Guidelines cite a VBAC success rate of 72-76%??


In the name of (stat) love, I want to make a really important point whilst you catch your breath…

The reported rate of VBAC in these cases IS NOT A VBAC SUCCESS RATE. This is simply the rate at which women in a defined cohort VBAC. Assuming these two things are synonymous is like thinking you can subsitute Cadbury for Pana (which, I assure you, you cannot).

A hypothetical

Take a group of 100 women who are potential chocolate connoisseurs. Sarah Wilson has successfully reached 66 of these women, so they have no interest in eating chocolate. 34 of them are after a sugar-fix and indicate they’d like to eat Pana, but 17 of them get Cadbury and the other 17 get Pana. The overall rate of Pana chocolate distribution is 17%, but the rate of successful distribution to the women who wanted it is 50%. So, whilst Pana sales aren’t as great as they could be, it’s maybe not so bad because half of the women who wanted Pana got their fix. (And, from Sarah’s perspective, these stats are looking pretty damn fine.)

Alternatively, here’s the chocolate-/sugar-/dairy-/gluten-/caffeine-/ramble-free breakdown:

Take a group of 100 women, 34 of them plan a VBAC and 17 of them go on to have a VBAC, this means:
– The VBAC rate for this group of 100 women is 17%
– The VBAC *success rate* for this group of women is 50%.

To make my point – taking the VBAC rate of 17% and describing it as a *success rate* is categorically incorrect. VBAC rates and VBAC success rates are *two different sets of stats*.

Furthermore, the group of women in this cohort are “women giving birth vaginally following a previous primary (first) caesarean section and having NO intervening pregnancies greater than 20 weeks gestation.” Do you fit the bill? If you’re having a VBA2C, this stat might be of little relevance to you. If you’re planning a second or third VBAC, you might also feel the need to find this information via other avenues.

So, how do we find out more about VBAC success rates? Well, until our health bureaucrats start recording how many women *attempt VBAC*, we will not know what the success rate is. The best thing you can do here is to ask your care provider AND hospital two questions:

– What is your VBAC rate?
– What is your VBAC success rate? (Otherwise known as ‘How many women in your care attempt VBACs? How many of these go on to VBAC?)

Further Food For Thought

Once you have a VBAC success rate, is it going to satisfy your craving for reassurance? Possibly, but maybe not.

Think about this: if an obstetrician has an 80% success rate, he/she sounds like a keeper, yeah? What about if this obstetrician only oversaw 5 attempted VBACs in one year, 4 of which were successful (hence the 80% success rate)? Does the stat indicate this care provider is skilled and experienced at attending VBAC, or does it simply suggest that this care provider lucked out? And, just whose ‘success’ is this stat, anyway?

The message you can take home in a foil swan

Stats are great to help us get our heads around the unknown, to get a feel for birth culture and to play to our best odds. But, it is really important to read the fine print – adding the word ‘success’ to what is simply a VBAC rate creates a BIG difference. Having the confidence to question stats, care providers and ‘birth experts’ takes intestinal fortitude, but seeking accurate information from a variety of sources makes for a balanced diet… Even if it is predominantly made up of Pana chocolate when you do the number-crunching!