Doldi 2006

Methods	Generation of the allocation sequence: not reported Allocation concealment method: not reported Blinding method: not reported Number and reasons for withdrawals: not reported ITT analysis: yes The authors did not provide additional information about allocation concealment and generation of allocation sequence methods Prospective randomised trial Metformin versus no treatment
Participants	40 PCOS participants were randomised (20 in the metformin group and 20 in the placebo group) Diagnosis of PCOS followed the Rotterdam criteria (ESHRE/ASRM) Exclusion criteria: a) congenital adrenal hyperplasia b) Cushing's syndrome c) androgen‐producing tumours d) hyperprolactinaemia e) thyroid dysfunction f) participant age older than 40 years g) FSH > 12 mIU/ml The causes of infertility were not reported Participants did not take any ovulation drugs or hormones for at least 3 months prior to the trial
Interventions	Group A was pretreated for 2 months with metformin 1.5 g/day until the embryo transfer day Protocol for controlled ovarian hyperstimulation: short‐protocol GnRH‐antagonist (cetrorelix acetate, Cetrotide®) with step up rec‐FSH (Gonal F® ‐ starting dose 150 IU). GnRH‐antagonist, cetrorelix acetate 0.25 mg/day, was started when the leading follicle reached 14 mm diameter on ultrasound scan and stopped on the day of hCG Recombinant hCG (Ovitrelle® 250 micrograms) was given when 2 or 3 follicles reached 16 mm in diameter on ultrasound scan. Oocyte retrieval was performed within 36 hrs of hCG injection. No more than 3 oocyte were fertilised (in accordance with Italian law) Assisted reproductive technology (ART): IVF Embryo transfer: maximum of 3 embryos were transferred per participant on day 2 after oocyte retrieval under abdominal US guidance Catheter used for transfer: not reported Luteal phase support: progesterone 90 mg (Crinone 8®) was given on the day of oocyte retrieval and was continued until menstruation or a positive pregnancy test
Outcomes	a) Number of ampoules of rec‐FSH b) Oestradiol levels c) Cancelled cycles d) Incidence of OHSS e) Number of mature oocytes
Notes	Country of the study: Italy
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Not stated
Allocation concealment (selection bias)	Unclear risk	Not stated
Blinding (performance bias and detection bias) All outcomes	Unclear risk	Not stated
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Reasons for withdrawals were not reported
Selective reporting (reporting bias)	Unclear risk	Live birth and clinical pregnancy rates were not assessed
Other bias	High risk	No power calculation. Neither the causes of infertility nor the baseline characteristics of the 2 groups were reported