Hauzman 2013.

Methods	Parallel group study. Number of women randomized: 100 (50 in each group). Number of withdrawals: 16 (7 in intervention group; 9 in control group). Number of women analyzed: 100 (ITT analysis).
Participants	Country: Spain. Inclusion criteria: aged 18‐38 years, regular normo‐ovulatory menstrual cycles (26‐35 days), BMI < 30 kg/m2, normal cycle day 3 basal serum hormone levels (FSH < 10 IU/L and oestradiol < 60 pg/mL) and < 3 previous IVF/ICSI attempts. Exclusion criteria: previous ovarian surgery, low ovarian response (cancellation of cycle due to poor follicular development after ≥ 7 days of gonadotropin stimulation or < 5 oocytes retrieved) in previous IVF/ICSI cycle and PCOS. Mean age ± SD: intervention group: 33.9 ± 3.4 years; control group: 34.5 ± 3.1 years. Setting: single hospital clinic in Madrid, Spain.
Interventions	Intervention: COCP: (ethinyl oestradiol 30 μg + levonorgestrel 150 μg) on day 1 or 2 of cycle prior to IVF/ICSI and continued for 12‐16 days, with stimulation starting 5 days after stopping pretreatment. Control: (oestradiol valerate 4 mg/day (2 mg × 2)) from day 20 of menstrual cycle for 5‐12 days until the day before starting stimulation. In both groups, GnRH antagonist (ganirelix 0.25 mg/day) started when the leading follicle reached 13 mm in diameter and ovarian triggering performed with rhCG (250 μg) (when 2 leading follicles reached ≥ 17 mm mean diameter).
Outcomes	Primary: Ongoing pregnancy rate. Secondary: Implantation rate. Clinical pregnancy rate. Miscarriage rate. Live birth rate.
Notes	Power calculation for sample size: yes but not achieved because this was a single‐centre study. ITT analysis: yes.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Computer‐generated random number list.
Allocation concealment (selection bias)	Low risk	Consecutively numbered opaque envelopes.
Blinding (performance bias and detection bias) All outcomes	Unclear risk	Although personnel involved in data collection and data analysis blinded it was not reported whether other personnel and participants were blinded.
Incomplete outcome data (attrition bias) All outcomes	Low risk	Reasons for withdrawals and proportions of withdrawals were fairly balanced between groups and data were analyzed on the basis of ITT.
Selective reporting (reporting bias)	Low risk	All prespecified outcomes reported.
Other bias	Low risk	Groups balanced at baseline with respect to demographic characteristics.