Yu S, et al. - A randomized controlled trial, including 516 first IVF/ICSI cycles, was performed to assess the utility of dydrogesterone (DYG) as an alternative progestin in a progesterone primed ovarian stimulation (PPOS) protocol. DYG exhibited no or only weak inhibition of ovulation in normal dosage and could serve as an hMG adjuvant during ovarian stimulation. Finding thus suggested a new possible utility of DYG: as an appropriate alternative progestin for a PPOS protocol in IVF.