Lok 2002.

Methods	Randomisation: computer‐generated Allocation concealment: sealed opaque envelopes Blinding of participants/investigators: no Blinding of assessors: no No. randomised: 110 No. analysed: 106 Intention‐to‐treat analysis: no Power and sample calculations described Duration of trial: not stated
Participants	Women undergoing transvaginal oocyte retrieval Mean age: 33 to 35 years Cause of infertility: tubal disease, male factor, endometriosis, anovulation, unexplained Women in control group 2 years younger than women in intervention group (P = 0.01); other baseline characteristics similar
Interventions	Control: patient‐controlled sedation and analgesia (IV propofol 10 mg/mL and alfentanil 40 mcg/mL) via a pump (N = 51) Intervention: physician‐administered sedation and analgesia with IV pethidine 1.5 mg/kg 5 to 10 minutes before oocyte retrieval (N = 55); additional pethidine 0.5 mg/kg given when necessary No premedication in either group
Outcomes	Primary: intraoperative and postoperative pain scores (VAS 0 to 100) Secondary: fertilisation, clinical pregnancy rate, patient satisfaction (VAS)
Notes	China Single centre Chinese University of Hong Kong Funding: not stated Loss to follow‐up (N = 4) in intervention group due to pump failure (n = 1) and personal reasons (n = 3) Definition of pregnancy not documented
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Computer‐generated
Allocation concealment (selection bias)	Low risk	Adequate: sealed envelopes
Blinding (performance bias and detection bias) All outcomes	Unclear risk	Blinding not possible owing to the nature of the interventions Blinding of assessors not reported
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Four lost to follow‐up (3%)
Selective reporting (reporting bias)	Low risk	All prespecified outcomes reported
Other bias	Unclear risk	Significant differences in age between the 2 groups Comparable infertility characteristics at baseline