Abstract: We found two RCTs suitable for inclusion in the review and six ongoing trials that have not yet reported results. Both included studies were published as abstracts in international conferences. Both studies were at unclear or high risk of bias for most of the seven domains assessed. Common problems were unclear reporting of study methods and lack of blinding. The main limitations in the overall quality of the evidence were high risk of bias and serious imprecision. There were no data on the primary outcomes of this review, namely live birth per woman randomised and miscarriage. Both studies reported clinical pregnancy rate: there was evidence of an effect between IVM and IVF, favouring the former (odds ratio 3.10, 95% confidence interval 1.06 to 9.00; 71 participants; 2 studies; I2 = 0%; very low-quality evidence). The incidence of OHSS was zero in both studies in both groups. There were no data for the other outcomes specified in this review. Though promising data on the in vitro maturation (IVM) technique have been published, unfortunately there is still no evidence from properly conducted randomised controlled trials upon which to base any practice recommendations regarding IVM before in vitro fertilisation (IVF) or intracytoplasmic sperm injection for women with polycystic ovarian syndrome. Regarding our secondary outcomes, very low-quality evidence showed that clinical pregnancy was higher with IVM when compared to IVF, whereas the incidence of ovarian hyperstimulation syndrome was zero in both studies in both groups. We are awaiting the results of six ongoing trials and eagerly anticipate further evidence from good-quality trials in the field.

Plain-language summary: We performed a comprehensive literature search of the standard medical databases (from database inception to 17 April 2018) in consultation with the Cochrane Gynaecology and Fertility Group Information Specialist, for all randomised controlled trials (studies in which participants are assigned to a treatment group using a random method) investigating the efficiency of IVM compared to conventional ART in subfertile women with PCOS. We searched for and included studies irrespective of language and country of origin. Two review authors independently selected and evaluated studies, extracted data, and attempted to contact the authors of studies for which data were missing. We found two studies (71 women), published as abstracts in international conferences, and six ongoing trials that met our inclusion requirements. Though promising data on the IVM technique have been published, unfortunately there is still no evidence concerning our primary outcomes of live-birth and miscarriage rates from properly conducted randomised controlled trials upon which to base any practice recommendations regarding IVM before ART for women with PCOS. Of the secondary outcomes specified in this review, very low-quality evidence showed that clinical pregnancy was higher when IVM was compared to conventional ART, whereas the incidence of ovarian hyperstimulation syndrome was zero in both studies in both groups. We are awaiting the results of six ongoing trials and eagerly anticipate further evidence from good-quality trials in the field. The quality of the evidence was very low for all outcomes.