Cartoon of pregnancy etiquette for childbirth adviceI used to think there was no question about this. Induction was the prologue to a long, hard labor that often wouldn't go well. And cesarean section was the (un)natural logical end of that. Simples.

In the early 1970s, induction got out of hand - over half of labors in the UK were induced. Then came a backlash. By the time I was having my first baby in the early '80s, labor induction was one of the stars of the "cascade of intervention" narrative of medicalized childbirth.

"Induction of labour may set off a 'cascade of intervention', and before you know it you may be drawn into having drips, electronic monitoring, epidurals and all the trappings of a medically complicated, high-tech birth." (National Childbirth Trust)

All in all, the history of trying to coax or prise overdue babies out has been dramatic and distressing. People have come up with very imaginative theories about how to get babies moving. I wrote a post about induction's colorful past - and present myths about what works - at this blog last year when the Royal baby watch went into overtime.

I wrote then that I thought the evidence on induction of labor and cesarean sections was reassuring, but the rate of induction was rising in the US - and we still didn't know enough about how women feel about inductions. That last part is a big deal, and unfortunately still true.

However this summer, the CDC reported that although the rate of induction had almost doubled between 1990 and 2010, it had started to reduce a little in 2011 and 2012. From its 2010 high of 23.8%, it eased down to 23.3% in 2012.

And I'm convinced the basic issue of whether or not induction of labor generally increases the rate of cesarean section has been settled. That's not because a major new trial has been reported. But a recent up-to-date analysis focusing just on this one question strengthens the case.

Meta-analysis result

Combined results of impact on cesarean section rate of labor induction, meta-analysis by Mishanina and colleagues, 2014 (click on image to go to the article)

Recently, Ekaterina Mishanina and colleagues published a wide-ranging meta-analysis on cesarean section and inductions. Their overall result is shown on the right. A meta-analysis is a way of analyzing the results of multiple studies at once. The diamond here incorporates 157 trials (mostly small ones). My introductory post on meta-analysis explains more.

Inductions decreased the rate of cesarean section by a few percent. That wasn't the case for everybody - not for women having preterm births, or with induction by amniotomy (breaking the bag of waters), for example. And it doesn't apply to women who have had a previous cesarean or are having twins, either.

The data have been grouped and analyzed by different groups of people looking at this question in different ways now. And the results have been consistent. (Key analyses are listed below.) That's not to say there aren't still other important questions about induction, especially for particular groups of women and their babies. There is a major NIH trial looking at the effects of induction of labor when babies are due, but not overdue. But it does seem that most women having inductions aren't increasing their chances of having a cesarean birth.

Induction now is a lot different than it was in the '70s. Routine ultrasound in pregnancy led to due dates being more accurate, which in turn reduced the number of inductions tried far too early for both the woman and her baby.

Prostaglandins helped, too. These hormones can ripen the cervix and increase the chances of the baby being born within 24 hours of starting the induction. Prostaglandins have led to a development that might turn out to improve the experience for women: using vaginal medication at home to prime the cervix, and only coming into hospital when you're in labor.

Cartoon of clinical trial Catch-22Despite that, induced labor's image as a leading culprit for excessive surgical childbirth is deeply rooted now. And we're not seeing major widespread dialing back of anti-induction rhetoric.

Maybe that's because many reputations and belief systems are built on it.

For a long time, the results of meta-analyses provided a scientific underpinning for those belief systems. What's more, the obstetric establishment's reluctance to accept those results - and to rigorously test enough of their preferred interventions - has been a core part of the critique of over-medicalized childbirth.

But accepting the message in these newer meta-analyses means a cherished, intuitively logical narrative for many of us starts to unravel at a core seam.

If you believe there should be a scientific basis for health care, then sometimes, evidence will challenge something you've believed wholeheartedly. That's where the rubber hits the road.


Here's information on pregnancy past the due date, as well as some older information for consumers on induction from the US Agency for Healthcare Research and Quality (AHRQ) - and the systematic review and meta-analysis on which it's based. More systematic reviews and meta-analyses looking at various aspects of the induction/cesarean section question that aren't mentioned in the post are: Wood and colleagues (2014), Gülmezoglu and colleagues (Cochrane, 2012), and from England's national guideline body (NICE, 2008).

In case you're wondering about my experience of pregnancy and childbirth, I've given birth twice (at home). I was a maternity consumer advocate for many years, and that was my entry point into epidemiological research. You can see my main scientific publications on care around pregnancy and childbirth here at Statistically Funny.

The cartoons are my own (Creative Commons License): more at Statistically Funny. And if you're interested in the origin of the phrase, "Mind your own beeswax," you might enjoy reading this.

* The thoughts Hilda Bastian expresses here at Absolutely Maybe are personal, and do not necessarily reflect the views of the National Institutes of Health or the U.S. Department of Health and Human Services.