Huirne 2006c.

Methods	Multicentre (8 IVF centres), parallel group study. Number of women recruited: 216. Number of women excluded: 34 (reasons not reported). Number of women randomized: 182 (91 in each group). Number of withdrawals: 22 (10 in intervention group: 1 due to hepatitis B, 1 due to non‐compliance, 1 due to personal reasons, 2 due to insufficient follicular response, 1 due to conversion to IUI, 1 due to absence of mature oocytes, 3 due to absence of viable embryos; 12 in control group: 2 due to spontaneous pregnancy, 3 due to failure of desensitisation, 1 due to personal reasons, 1 due to stimulation failure, 3 due to absence of 'mature' oocytes, 2 due to failure of fertilisation). Number of women analyzed: 182.
Participants	Country of authors: the Netherlands, Belgium, France and Austria. Inclusion criteria: regular IVF/ICSI indication, male partner with viable sperm in the ejaculate, aged 18‐39 years. Exclusion criteria: any previous ART cycles with < 3 oocytes or ≥ 3 consecutive ART cycles without a clinical pregnancy, any contraindication to ART, gonadotrophins or OCPs, significant systemic disease. Mean age ± SD: intervention group: 32.8 ± 3.8 years; control group: 32.2 ± 4.2 years.
Interventions	Intervention: COCP (ethinyl oestradiol 30 μg + levonorgestrel 150 μg daily), started within 5 days of onset of menses for 21‐28 days (stop on a Sunday) + r‐hFSH (150‐225 IU/day), started post‐treatment day 5 (= stimulation day 1) + GnRH antagonist (cetrorelix acetate 0.25 mg/day, SC), started stimulation day 6. Control: GnRH agonist (buserelin acetate 500 μg/day, SC), started cycle day 18‐22 (reducing dose to 200 μg/day when downregulation was achieved) + r‐hFSH (150‐225 IU/day), started when downregulation was achieved. After 5 days of r‐hFSH treatment, the dose could be adjusted by steps of 75 IU (maximal dose 450 IU/day), according to the ovarian response. Both rhFSH and GnRH analogues were continued until hCG injection, administered when the largest follicle reached a mean diameter ≥ 18 mm and ≥ 2 other follicles had a mean diameter ≥ 16 mm.
Outcomes	Ongoing pregnancy rate: positive heart activity at a gestational age of 12 weeks. Clinical pregnancy rate: presence of ≥ 1 foetal sacs with or without heart activity confirmed with ultrasound, performed at least 4 weeks after embryo transfer. Numbers of oocytes retrieved per woman. Multiple clinical pregnancies. Total number of oocyte retrievals performed on weekends or public holidays. Cancellation rate. Drug requirements. Total number of (good quality) embryos. Implantation rate.
Notes	Power calculation performed: yes. ITT analysis performed: no.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote: "182 were randomly allocated to...", "The treatment assigned to each patient was determined according to a computer‐generated concealed randomization list. Randomization was performed by centre."
Allocation concealment (selection bias)	Unclear risk	"Concealed randomization list," method not reported.
Blinding (performance bias and detection bias) All outcomes	Unclear risk	Not reported.
Incomplete outcome data (attrition bias) All outcomes	Low risk	All women randomized were included in final analysis.
Selective reporting (reporting bias)	Low risk	Data on all planned outcomes reported.
Other bias	Low risk	No significant difference in baseline characteristics with regard to age, race, duration of infertility, cause of infertility, smoking habits, primary infertility, number of previous ART attempts, number of follicles, endometrial thickness, FSH levels and oestradiol levels. P value of BMI was 0.04.