A recently accepted study demonstrated that raised progesterone levels can be normalized through administration of a GnRH antagonist during three subsequent days prior to the start of gonadotropin stimulation in a GnRH antagonist protocol. This regimen, after normalisation of the progesterone value, allows controlled ovarian hyperstimulation (COH). Since this regimen is valid in case of elevated progesterone, GnRH antagonists pretreatment may prove to be a valid tool for scheduling IVF treatment in patients with normal progesterone values on day 2 of the cycle. In this prospective randomised trial, the investigators study the impact of administration of a GnRH antagonist during 3 consecutive days at initiation of the cycle.