GNRH1 and pregnancy disorder: Although our results support the benefit of the addition of GnRH agonists during the luteal phase, which has been reported in several previous meta-analyses [3, 35, 52], such a benefit, if present, is unlikely to promote the application of GnRH agonists in clinical practice until their safety (including both adverse perinatal outcomes and congenital malformations) can be confirmed in future studies.