This large prospective , randomized study was designed to compare the `` mild '' protocol with clomiphene citrate , low-dose gonadotropins and a GnRH-antagonist ( CC/Gn/GnRH-ant protocol ) with the `` long '' protocol with a GnRH-agonist and high-dose Gn for the controlled ovarian hyperstimulation ( COH ) of patients with expected poor ovarian responsiveness undergoing IVF .