The Phase 3 ESTHER-1 trial demonstrated follitropin delta to be an efficacious and well-tolerated treatment for ovarian stimulation (OS), with a reduced risk of OHSS and a reduced need for gonadotropin-releasing hormone (GnRH) agonist as a preventive intervention for OHSS compared with follitropin alfa (11, 17). The gene discussed is GNRH1; the disease is ovarian hyperstimulation syndrome.