Two-arm randomised, single-centre, controlled open-label trial. Summarily, women undergoing exogenous gonadotropin ovarian stimulation for ART in a gonadotropin-releasing hormone (GnRH) antagonist down-regulated cycle and at high risk for ovarian hyperstimulation syndrome (OHSS) will be included in either the control ("fresh embryo transfer") or intervention ("subsequent vitrified-warmed embryo transfer") groups. Women in the control group will undergo GnRH agonist triggering followed by intensified luteal phase support while the intervention group will electively vitrify all viable embryos after GnRH triggering and perform the embryo transfer (ET) in a subsequent unstimulated cycle.