Ye 2009.

Methods	Parallel group study. Number of women randomized: 220 (109 in intervention group; 111 in control group). Number of withdrawals: none reported. Number of women analyzed: 208 cycles (103 in intervention group; 105 in control group) and numbers of cycles were equivalent to numbers of participants.
Participants	Country: China. Inclusion criteria: aged 25‐35 years; BMI 18‐25 kg/m2; number of previous IVF cycles < 3, and no previous poor response to ovarian stimulation (poor ovarian response characterised by cancellation of the cycle due to either poor follicular development or ≤ 4 cumulus‐oocyte‐complexes collected at oocyte retrieval); normal ovulatory cycles (25‐35 days); both ovaries present and normal uterus; no hormone therapy within the past 3 months; no current or past diseases affecting ovaries, gonadotrophin, sex steroid secretion, clearance or excretion. Exclusion criteria: not explicitly reported. Age range: 25‐35 years. Setting: IVF centre, China.
Interventions	Intervention: oral oestradiol valerate (4 mg/day) preceding the IVF cycle from day 21 until day 2 of next cycle before GnRH antagonist protocol. Control: standard long GnRH agonist protocol.
Outcomes	Number of oocytes collected. MII oocytes. Fertilisation. Implantation. Live birth. Early pregnancy rate. Clinical pregnancy rate. OHSS rate. Hormone profiles.
Notes	Outcomes measured as per 'embryo transfer cycle' but numbers of cycles transferred were equivalent to numbers of women randomized. Power calculation for sample size: not reported. ITT analysis: not reported.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	"Randomization allocation sequence was generated from a table of computer‐generated random numbers."
Allocation concealment (selection bias)	Unclear risk	Not reported.
Blinding (performance bias and detection bias) All outcomes	High risk	"This study was not blind."
Incomplete outcome data (attrition bias) All outcomes	Low risk	No withdrawals reported, cycle cancellation (number of cycles were equivalent to numbers of women randomized) similar between groups.
Selective reporting (reporting bias)	Low risk	All prespecified outcomes reported.
Other bias	Low risk	Groups comparable at baseline with respect to demographic characteristics.

17‐βE₂: 17‐beta oestradiol; AMH: anti‐mullerian hormone; BMI: body mass index; COCP: combined oral contraceptive pill; COH: controlled ovarian hyperstimulation; COS: controlled ovarian stimulation; FSH: follicle‐stimulating hormone; rFSH: recombinant follicle‐stimulating hormone; GnRH: gonadotrophin‐releasing hormone; GnRHa: gonadotrophin‐releasing hormone analogue; hMG: human menopausal gonadotrophin; IM: intramuscular; ITT: intention to treat; IU: international unit; IUI: intrauterine insemination; IVF: in vitro fertilisation; IVF‐ET: in vitro fertilisation with embryo transfer; LH: luteinising hormone; OCP: oral contraceptive pill; OHSS: ovarian hyperstimulation syndrome; PCOS: polycystic ovary syndrome; PO: per os (oral); rhCG: recombinant human chorionic gonadotropin; SC: subcutaneous; SD: standard deviation; SEM: standardized mean difference; TESE: testicular epididymal sperm extraction; WHO: World Health Organization.