OTHER
Doustim protocol
In Duostim group, the follicular stimulation will be started with a fixed dose of 150 IU of rFSH and HMG 75 IU for 4 days. Daily administration of a GnRH antagonist will be started when the leading follicle are 13-14mm in diameter and continue until the day of the trigger of the ovulation. Five days after the first oocyte retrieval second gonadotropin stimulation will be started identical to the first one..