Power of this trial
This trial was well conducted according to its protocol. Although the planned accrual target was achieved, the optimistic power calculation assumptions and the losses through protocol violations reduce the reliability of this trial.
The potential effects of the lack of blinding
Studies have shown that patients who believed an intervention was helpful would seek an effect even if the intervention has been proven to do harm, with no evidence of efficacy (N Engl J Med 1999;341:992–6). The lack of blinding in this trial has exposed participants to potentially profound placebo effects. The hypnosis group reported a more positive birth experience and would choose to use antenatal hypnosis again in future.
Was the outcome measure appropriate?
This study aimed to investigate whether antenatal hypnosis reduced the use of analgesia; however, other potential beneficial effects of hypnosis, e.g. the potential to delay the need of analgesia in labour, may also be relevant.
Does yoga help to select patients who may benefit from hypnosis?
Despite not being detailed in the registered protocol, the authors explored the relationship between mothers who practised yoga with those who did not. Although different patient groups may react differently to the same hypnosis training, this trial was not designed to answer this question.
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