Meta-analysis of GnRH antagonist protocols: do they reduce the risk of OHSS in PCOS?

This systematic review and meta-analysis investigated whether gonadotrophin-releasing hormone (GnRH) antagonist protocols reduce the risk of ovarian hyperstimulation syndrome (OHSS) in women with polycystic ovary syndrome undergoing IVF compared with the long agonist protocol. Searches were conducted on MEDLINE, EMBASE, Cochrane Library, National Research Register and ISI Conference Proceedings. Primary outcome was OHSS incidence. Secondary outcomes were total duration and dose of gonadotrophin, number of oocytes retrieved and clinical pregnancy and miscarriage rates. A total of 966 women were included in nine randomized controlled trials. There was inconsistency in definition, classification of severity and reporting of the OHSS rate. There was no difference in the incidence of severe OHSS in the antagonist group compared with the long agonist group (relative risk 0.61; 95% CI 0.23 to 1.64). However, when all moderate and severe OHSS cases were pooled, the antagonist protocol was associated with significantly lower risk of OHSS (relative risk 0.60; 95% CI 0.48-0.76; P<0.0001). A possible reduction in the incidence of severe OHSS with the GnRH antagonist protocol should be viewed with caution since the data is inconclusive. Larger randomized trials with adequate sample size and standardized definition, classification and diagnosis of OHSS remain necessary.