Zheng 2012.

Methods	Randomised controlled study 82 women who were undergoing IVM cycles were randomised to 10,000 units hCG priming (N = 40) or no priming (N = 42)
Participants	The participants all met the Rotterdam criteria for the diagnosis of polycystic ovarian syndrome. The age of the women ranged from 24 to 39 years; mean 30.2 years). "Basic patient characteristics, including mean female age, body mass index (BMI), and baseline FSH did not differ between the hCG primed (40 women) and the non‐primed (42 women) groups."
Interventions	10,000 units hCG priming 36 to 38 hours prior to oocyte collection or no priming
Outcomes	No. of oocytes retrieved Oocyte maturation rate at 32 hours No. of oocytes fertilised No. of oocytes cleaved Cycles with embryo transfer No. of embryos transferred Implantation rate Clinical pregnancy rate (presence of an intrauterine gestational sac on ultrasound on day 35 after embryo transfer) Live birth rate Miscarriage rate (pregnancy loss after ultrasonographic evidence of an intrauterine pregnancy) No. of cycles with embryo freezing
Notes	Funded by National Science Fund for Distinguished Young Scholars and State Basic Research Development Program of China. No competing interests declared. Author contacted but no response.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Treatment allocated using a "computerised random table"
Allocation concealment (selection bias)	Unclear risk	Not reported.
Blinding of participants and personnel (performance bias) All outcomes	High risk	" The patients and the embryologist were blind to the randomised results." Comment: Patients unable to be blinded as were either receiving hCG priming by subcutaneous injection followed by oocyte collection 36 to 38 hours post priming or no hCG injection and immediate oocyte collection. There was no placebo used.
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Embryologist "blind to the random results" Comment: No explanation as to how the embryologists were blinded. No comment on blinding of other assessors e.g. sonographers, clinicians
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Withdrawals not reported.
Selective reporting (reporting bias)	Unclear risk	Study protocol not available to check whether outcomes were prespecified
Other bias	Low risk	Funding stated and no competing interests declared. No significant difference reported in basic patient characteristics between the two groups.

PCOS = polycystic ovarian syndrome

IVM = in vitro maturation

hCG = human chorionic gonadotrophin

IVF = in vitro fertilisation

ICSI = intracytoplasmic sperm injection

PCO = polycystic ovaries

FSH = follicle stimulating hormone