Harmon 1990.

Methods	Quasi‐randomised controlled trial conducted in a USA hospital setting.
Participants	60 women participated in this trial, 30 in each arm. Inclusion criteria: "women ranging in age from 18 to 35 years, nulliparous, married, white, during the end of the second trimester of pregnancy. No reported history of (1) psychiatric hospitalisation, (2) depression during pregnancy, or (3) obstetric risk (e.g. miscarriage, pre‐eclampsia, diabetes, etc.). The study did accept women with borderline hypertension".
Interventions	Experimental group: antenatal preparation was "conducted over six 1‐hour weekly sessions". Participants in the hypnosis group "heard the live hypnotic induction during Session 1 and heard the taped induction at the beginning of Sessions 2‐6". Women were then given 2 trials of an IPT using the dominant arm. Women were also given a cassette tape recording of the hypnotic induction and told to practice daily. Control group: "antenatal preparation was "conducted over 6 1‐hour weekly sessions". Control participants "listened to the control tape at the beginning of each treatment session". Women were then given 2 trials of the same IPT. Women were "given a cassette tape recording of 'Practice for Childbirth'" and told to practice daily. "Control tapes contained standard neuromuscular relaxation exercises in which women were asked to let go of tension in sequential muscle groups." Antenatal preparation began "in the early portion of the third trimester" and the sessions included up to 15 women. Both groups attended 6 childbirth education classes provided by their physicians.
Outcomes	Pain intensity (measured on the McGill Pain Questionaire Present Pain Intensity Scale where 0 = No pain, 1 = Mild, 2 = Discomforting, 3 = Distressing, 4 = Horrible, 5 = Excruciating); postnatal depressive symptoms (Depression scores on Minnesoto Mulitphasic Personality Inventory (MMPI) Depression Scale); Apgar score < 7 at 5 minutes; length of labour; spontaneous vaginal birth; use of pharmacological pain relief; caesarean section. Hypnotisability was also measured using the Harvard Group Scale of Hypnotic Susceptibility. High hypnotisability was defined as a score greater than or equal to 7 and low hypnotisability was defined as a score < 7.
Notes
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	High risk	Quasi‐randomised controlled trial ‐ "Assignment to one of the two treatment groups (hypnosis or control) was based solely on the month the woman was expected to deliver".
Allocation concealment (selection bias)	High risk	Quasi‐randomised controlled trial ‐ "Assignment to one of the two treatment groups (hypnosis or control) was based solely on the month the woman was expected to deliver".
Blinding of participants (objective outcomes)	Low risk	“Subjects were not informed that there were two treatment conditions; all were told that they would be receiving additional specialized childbirth training.”
Blinding of participants (subjective outcomes)	Unclear risk	Women not told their group allocation but there was no reporting about whether blinding was successful.
Blinding of personnel (performance bias)	Unclear risk	Not reported.
Blinding of outcome assessment (detection bias) All outcomes	Low risk	“blind ratings” noted as part of discussion of shortcomings of previous studies where the outcomes were not blinded.
Incomplete outcome data (attrition bias) All outcomes	Low risk	3 women excluded because each had 1 or more pre‐treatment scores > 70 on the MMPI and 1 woman excluded due to caesarean section.
Selective reporting (reporting bias)	Low risk	All prespecified outcomes reported upon.
Other bias	Unclear risk	No baseline demographic characteristics table presented.