GNRH1 and ovarian hyperstimulation syndrome: In two phase 3 trials investigating corifollitropin alfa (100 or 150 μg) as part of a GnRH antagonist COS protocol, rates of moderate-to-severe OHSS were 3.4–4.1 %, compared with 1.6–2.7 % in patients receiving recombinant FSH [30,31].