This is randomized clinical trial studying two luteal support protocols of In vitro fertilization patients (IVF) treated by a GnRH antagonist (GnRH ant) protocol and are at risk of developing ovarian hyperstimulation syndrome (OHSS). The randomization procedure will be performed by a third party in the hospital by using a randomization table: patients fulfilling the inclusion and exclusion criteria and giving their informed consent will be randomized into one of two arms. This study does not include any intervention affecting the ovarian stimulation and is solely intended to test the post ova pickup period.