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Induction increases Caesareans

August 24, 2013

No it doesn’t

According to this forthcoming paper in BJOG, induction of labour may even reduce the risk of needing a Caesarean delivery.  Click here for the online pre-print.  Or here wood et al BJOG 2013

This is a surprise because most people have long assumed the opposite. Induced labours often end up with Caesareans, because  the labour never starts, or it goes on so long that the mother becomes exhausted or the baby develops fetal distress, and Caesarean rates for women with induced labours are generally higher than for those who go into labour on  their own.  Over the 1970s and early 1980’s when labour induction became popular, Caesarean rates also rose. Unsurprisingly pretty much everyone believed that induction was a factor. Labour induction rates became one of the battlegrounds between proponents of natural childbirth and those who supported more interventionist policies.

But labour is induced for a reason; because the pregnancy is overdue, the mother had raised blood pressure, or the baby is worryingly big, or small.  If such problem pregnancies had been left alone perhaps they would have had even more Caesareans.  Perhaps the rise in Caesarean rates over the 1970s had another cause; maybe doctors and parents just became less willing to take even small risks with their pregnancies.

The only way to prove causation is to do trials in which women are allocated at random to either have labour induced, or to be left alone to await it starting on its own.  These are difficult – I was involved in some – but they were done.  Some showed a slight increase in Caesareans, and some a slight decrease, but mostly the differences seen were compatible with the effect of chance – the trials were too small.  But now a group from Canada have pulled them all together.

wood fig 2

This figure summarises all the trials. For almost all the individual ones the 95% confidence interval around the odds ratio includes unity, so the result may well have occurred by chance. But overall labour induction reduces the need for Caesarean by nearly 20% (odds ratio 0.83, 95% confidence interval 0.76-0.92). This is unlikely to be due to chance.

Of course there are caveats, and the authors are appropriately cautious in claiming that they’ve proven that labour induction prevents Caesareans.  But their best guess remains, that in settings like the ones where the trials were done, i.e. hospitals in the developed world over the last 30 years or so, labour induction, done for a legitimate medical reason, is very unlikely to increase Caesarean rates and probably slightly reduces them. I think they’re right.

This is an important message for obstetricians and midwives.

Jim Thornton

9 Comments leave one →
  1. December 15, 2013 9:39 pm

    the caveat there is “if done for a legitimate medical reason”, which is without argument, but can that be said of all inductions?

    • December 16, 2013 7:31 am

      Good point. But do we need an RCT of every possible indication for induction, or is it reasonable to extend the indications somewhat right now, without more trials? I think the latter, with one exception. It would be a big jump to offer universal induction at term without decent trial evidence.

  2. Tracey Cooper permalink
    January 18, 2014 8:45 pm

    Sends a message to women and the whole population that birth has to be controlled is a medical process. Why can’t we just wait for nature to do its thing? That’s what women’s bodies do…….they do it well!
    Tracey x

  3. November 9, 2014 7:27 pm

    The number of systematic reviews saying the same thing, namely that induction reduces CS, is rising all the time.

    Here are links to three more. Courtesy of Hilda Bastian’s blog here.

    Almost time for these systematic reviewers to do some primary research!

  4. November 23, 2014 5:11 pm

    maybe I’m not reading them correctly but looking at the Hospital Episode stats, when labour starts spontaneously the CS rate is around 11%, when either medically or surgically induced it is 22-24%. Can you explain that please?

    • November 23, 2014 6:48 pm

      In the HES dataset labour was induced for a reason; post-maturity, diabetes, fetal growth restriction, fetal macrosomia, hypertension, etc. Some (probably all) of the increase in CS in that dataset was due to the reason the pregnancy was induced.

      The RCT participants had the same risk factors in both arms, so there were no extra Caesareans caused by the underlying pathology in the induction group.


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