Prospective, open, randomised, parallel, multicentre, two arm trial comparing a new form of luteal support (S.C.) to an approved comparator (vaginal gel).

Inclusion Criteria:

• Age 18- 42 (upon starting COH);
• BMI <30 kg/m2;
• <3 prior ART cycles (IVF, ICSI and related procedures);
• Baseline (day 2-3 of cycling) FSH <15 IU/L and E2 <80 pg/mL;
• Normal uterine cavity as per recent hysterosalpingogram, sonohysterogram or hysteroscopic exam (i.e. no polyp or protruding sub-mucosal fibroid);
• At least 3 retrieved oocytes;
• Patient has given written informed consent.

Exclusion Criteria:

• Intramural uterine fibroids that distort the uterine cavity or polyps >1 cm;
• Stage III or IV endometriosis (endometriomas);
• Hydrosalpinx;
• History of past poor response to COH resulting in canceling ART;
• Use of thawed/donated oocytes;
• Use of thawed/donated embryos;
• Patients affected by pathologies associated with any contraindication of being pregnant;
• Hypersensitivity to study medication;
• Uncontrolled adrenal or thyroid dysfunction;
• Undiagnosed vaginal bleeding;
• History of arterial disease;
• Patients with hepatic impairment;
• Neoplasias (current) or history of neoplasia that may be responsive to progesterone;
• High grade cervical dysplasia;
• Active thrombophlebitis or thromboembolic disorders, or a history of hormone-associated thrombophlebitis or thromboembolic disorders;
• History of recurrent pregnancy loss defined as 3 or more spontaneous miscarriages wherein pregnancy developed to a minimum of a gestational sac on TVUS;
• Participation in a concurrent clinical trial or another trial within the past 2 months;
• Use of concomitant medications that might interfere with the study evaluation;
• Pre-implantation genetic diagnosis/screening.