Onalan 2005

Methods	Generation of the allocation sequence: computer randomisation system Allocation concealment method: not reported Blinding method: yes Number and reasons for withdrawals: reported ITT analysis: no Prospective, randomised, double‐blind, placebo‐controlled trial Metformin versus placebo
Participants	110 PCOS participants without concomitant causes of infertility Diagnosis of PCOS followed the Rotterdam criteria (ESHRE/ASRM) 2 participants withdrew for personal reasons 108 participants were randomised (53 in the metformin group and 55 in the placebo group) Participants < 40 years Both groups were matched for age, duration of infertility, BMI and insulin resistance All other causes of hyperandrogenism were ruled out before diagnosis of PCOS Exclusion criteria: previous treatments with hormonal medications and insulin‐lowering agents in the last 3 months
Interventions	Metformin 850 mg bid or tid (according to BMI) for 8 weeks before their first ICSI cycle, through the luteal phase and until a positive pregnancy test Protocol for controlled ovarian hyperstimulation: long luteal phase pituitary down‐regulation using the GnRH analogue triptorelin 0.1 mg (Decapeptyl®) with rec‐FSH (Gonal F® starting dose of 150 IU or 300 IU). Oocyte retrieval was performed within 36 hours after hCG injection (Pregnyl® 10000 IU) Assisted reproductive technology (ART): ICSI Embryo transfer: maximum of 3 embryos were transferred per participant on day 3 after oocyte retrieval A selective assisted hatching procedure with laser was used if the participant was > 35 years, the zona pellucida was considered to be thick, abnormally shaped zona, and excessive fragmentation or slowly developing embryos were noted Catheter used for transfer: not reported Luteal phase support: not reported
Outcomes	a) Number of days of gonadotrophins b) Number of ampoules of gonadotrophins c) Number of follicles (> 16 mm) d) Number of mature oocytes e) Fertilisation rate f) Number of embryos transferred g) Pregnancy rate per woman h) Clinical pregnancy rate per woman i) Miscarriage rate j) Serum E2 levels k) Glucose/insulin rate l) Incidence of OHSS
Notes	Country of the study: Turkey
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Adequate ‐ computer randomisation system
Allocation concealment (selection bias)	Unclear risk	Not stated
Blinding (performance bias and detection bias) All outcomes	Low risk	Double‐blinded
Incomplete outcome data (attrition bias) All outcomes	High risk	Intention‐to‐treat (ITT) was not performed
Selective reporting (reporting bias)	Unclear risk	Live birth rate was not reported
Other bias	Low risk	Power calculation was not performed. There were no significant differences in the baseline characteristics of the participants between the 2 groups