title: Gonadotrophin-releasing hormone antagonists for assisted reproductive technology.
abstract: BACKGROUND
  Gonadotrophin-releasing hormone (GnRH) antagonists can be used to prevent a luteinizing hormone (LH) surge during controlled ovarian hyperstimulation (COH) without the hypo-estrogenic side-effects, flare-up, or long down-regulation period associated with agonists. The antagonists directly and rapidly inhibit gonadotrophin release within several hours through competitive binding to pituitary GnRH receptors. This property allows their use at any time during the follicular phase. Several different regimes have been described including multiple-dose fixed (0.25 mg daily from day six to seven of stimulation), multiple-dose flexible (0.25 mg daily when leading follicle is 14 to 15 mm), and single-dose (single administration of 3 mg on day 7 to 8 of stimulation) protocols, with or without the addition of an oral contraceptive pill. Further, women receiving antagonists have been shown to have a lower incidence of ovarian hyperstimulation syndrome (OHSS). Assuming comparable clinical outcomes for the antagonist and agonist protocols, these benefits would justify a change from the standard long agonist protocol to antagonist regimens. This is an update of a Cochrane review first published in 2001, and previously updated in 2006.
  
  
  OBJECTIVE
  To evaluate the effectiveness and safety of gonadotrophin-releasing hormone (GnRH) antagonists compared with the standard long protocol of GnRH agonists for controlled ovarian hyperstimulation in assisted conception cycle.
  
  
  METHODS
  We performed electronic searches of major databases, for example Cochrane Menstrual Disorders and Subfertility Group Specialized Register, CENTRAL, MEDLINE, EMBASE (from 1987 to April 2010); and handsearched bibliographies of relevant publications and reviews, and abstracts of major scientific meetings, for example the European Society of Human Reproduction and Embryology (ESHRE) and American Society for Reproductive Medicine (ASRM).
  
  
  METHODS
  : Two review authors independently screened the relevant citations for randomized controlled trials (RCTs) comparing different agonist versus antagonist protocols in women undergoing IVF or ICSI.
  
  
  METHODS
  Two review authors independently assessed trial risk of bias and extracted data. If relevant data were missing or unclear, the authors were contacted for clarification.
  
  
  RESULTS
  Forty-five RCTs (n=7511) comparing the antagonist to the long agonist protocols fulfilled the inclusion criteria. There was no evidence of a statistically significant difference in rates of live-births (9 RCTs; odds ratio (OR) 0.86, 95% CI 0.69 to 1.08). There was a statistically significant lower incidence of OHSS in the GnRH antagonist group (29 RCTs; OR 0.43, 95% CI 0.33 to 0.57).
  
  
  CONCLUSIONS
  The use of antagonist compared with long GnRH agonist protocols was associated with a large reduction in OHSS and there was no evidence of a difference in live-birth rates.