Roy 2012.

Study characteristics
Methods	Randomised clinical trial Duration and location of the trial: quote: "This prospective randomized controlled trial was performed at a tertiary care hospital from January 2005 to January 2010.“
Participants	Inclusion criteria: women aged 20‐35 years having infertility for > 1 year, BMI < 28, and with anovulatory PCOS based on the Rotterdam 2003 criteria Exclusion criteria: quote: "in all patients, a comprehensive infertility work‐up was done. This included a tubal patency test, pelvic ultrasonography, husband semen analysis, and serum hormone measurements (FSH, LH, prolactin, estradiol, progesterone, and testosterone) on the 2nd to 5th day of the cycle. Patients having abnormality in any of these tests, which may be responsible for reproductive failure, were excluded from the study." Number of centres: 1, a tertiary care hospital in India Number of women randomised: 212 women; group A letrozole: 104, group B CC: 108 Number of women analysed: letrozole group: 98, CC group: 106 Number of withdrawals/exclusions/loss to follow‐up and reasons: 8 lost to follow‐up Age (y): group A letrozole: 26.1 ± 1.8, group B CC: 26.5 ± 1.3 BMI (kg/m²): group A letrozole: 25.8 ± 2.1, group B CC: 25.4 ± 1.6 Duration of infertility (y): group A letrozole: 6.4 ± 3.8, group B CC: 5.8 ± 3.1 Country: India
Interventions	Group A: letrozole, orally given in doses of 2.5 mg/day and 5 mg/day for 5 days during cycle days 3‐7 Group B: CC, orally given in doses of 50 mg/day and 100 mg/day for 5 days during cycle days 3‐7 Treatment was continued for 3 months.
Outcomes	Mean number of follicles, endometrial thickness, ovulatory cycle rate, conception rate, pregnancy outcome, miscarriage rate, multiple pregnancies and OHSS rate
Notes	Ethical approval: yes, the necessary ethical approval was taken from Institutional Review Board to conduct this trial. Informed consent: yes, the participants were counselled, and informed consent was taken before randomisation. Source of funding: quote: “Source of support: Nil, Conflict of interest: None declared.” Power calculation: quote: "On basis of previous studies, to achieve a statistically valid comparison of pregnancy rates in the two groups, with a type I error of 0.05 and a power of 80%, a sample size of at least 40 women in each arm was required." We contacted Dr Roy by email to get additional information, but he did not respond.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Online software was used to generate a random‐number table (www.randomization.com).
Allocation concealment (selection bias)	Unclear risk	Quote: "Randomisation codes (A, B) were packed into sealed opaque envelopes by an individual not involved in enrolment, treatment and follow‐up of subjects to ensure concealment of allocation. One resident had the responsibility for dispensing the trial drugs to the patient based on the unique randomisation code. At the end of allocation, the resident provided us with a randomisation list."
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	Not stated
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Not stated
Incomplete outcome data (attrition bias) All outcomes	Low risk	8 losses to follow‐up of 112 participants
Selective reporting (reporting bias)	Low risk	All expected outcomes reported
Other bias	Low risk	None