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June 16, 2015

The third recent negative self-hypnosis in labour trial

Self-hypnosis is a popular method of pain relief in labour; it sounds like a good idea, it’s cheap, could probably be taught to many women, and is unlikely to have serious adverse side effects.  But until recently there were only poor quality trials.  Now suddenly there is a glut of good ones.

In 2014 we commented on two, a Danish trial (click here) and the Australian HATCH trial (click here). Both were prospectively registered, with a predefined primary endpoint, (epidural in the Danish trial, epidural or opiates in HATCH), hit their predetermined sample size and analysed everyone in an unbiased way, by intention to treat. Both were negative.

Now my friend Professor Soo Downe from Preston in Lancashire has reported on a third one, the Self Hypnosis in Pregnancy (SHIP) trial. Click here for the full report.

Again it was beautifully designed and conducted. Prospectively registered here.  (The link states it was retrospective, but this seems to be a fault with the recently updated website; SHIP was registered well before any codes were broken or analysis was done.) The primary outcome was epidural use, and the planned sample size 300 per group. 680 women were eventually randomised (343 to self-hypnosis and 337 to control) and all were followed-up. Epidural use was 94/343 (28%) in the self-hypnosis group v. 101/337 (30%) in controls, odds ratio (OR) 0.89, 95% confidence interval (CI) 0.64–1.24. i.e. the self-hypnosis does not work.

The authors also measured 29 allegedly predetermined (only 10 were listed on the trial registration site) secondary outcomes of which 27 were not statistically significantly different. For some reason they were placed in a supplementary appendix; come on you BJOG editors, get your act together! Some slightly favoured self-hypnosis, e.g. breast feeding 44% v 39% OR 1.23, 95% CI 0.82 – 1.86, or prolonged neonatal admission 6.2% v 6.6%. OR  0.94, 95% CI 0.50-1.74). Others slightly favoured controls, e. g. Caesarean deliveries 25% v 23 %, OR 1.11, 95% CI 0.78-1.58), and three of the 4 stillbirths were in the self-hypnosis group. But none were statistically significant. Nor were there any significant differences in anxiety, depression or “impact of events” scores at 2 and 6 weeks postnatal. This is a clearly negative trial.

However, the authors (or BJOG) provided a tweetable abstract:

“Going to 2 prenatal self-hypnosis groups didn’t reduce labour epidural use but did reduce birth fear & anxiety postnatally at < £5 per woman”.

This is misleading. Self-hypnosis did not reduce fear & anxiety postnatally.  It may have made a difference in the change in anxiety level between before and after labour and in the change in fear of birth between the two time periods, but these are very odd trial outcome measures. You can’t be anxious or fearful about birth after it has occurred. More importantly the change measures were not pre-specified among the secondary outcomes, they are dependent on a low postnatal response rate which was higher in the intervention than the control group, and the baseline scores for both measures were non-significantly higher in the hypnosis group at baseline, so some of the change is likely to be due to regression to the mean, i.e nothing to do with the treatment.  At best the change scores are hypothesis generating for future studies.

Here’s a better tweetable abstract:

SHIP is the 3rd well-designed RCT to show that self-hypnosis is ineffective for pain relief in labour. But it is cheap & harmless.

Jim Thornton

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