Inclusion Criteria:

• Patient has given written informed consent;
• BMI < 30 kg/m2;
• Age 18 - 42 (upon starting COH);
• <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, sonohystogram or hysteroscopic exam (i.e. no polyps or protruding submucosal fibroids);
• Patients must have at least three retrieved oocytes.

Exclusion Criteria:

• Intramural uterine fibroids that distort the uterine cavity or polyps >1 cm;
• Stage III or IV endometriosis (no endometriomas);
• Hydrosalpinges;
• History of past poor response to COH resulting in canceling ART;
• Use of thawed/donated oocytes;
• Use of thawed/donated embryos;
• Gestational carrier;
• Patients affected by pathologies associated with any contraindication of being pregnant;
• Hypersensitivity to study medication;
• Uncontrolled adrenal or thyroid dysfunction;
• History of conditions (i.e. toxic shock syndrome) that would contraindicate use of a vaginal progesterone product;
• History of arterial disease;
• Patients with hepatic impairment (liver function tests > 2x upper limits of normal);
• Patients with dermatologic disease;
• Patients with renal impairment (estimated creatinine clearance <60 mL/min/1.73 m2);
• Neoplasias (current) or history of neoplasia that may be responsive to progesterone;
• High grade cervical dysplasia;
• 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 in another trial within the past 2 months;
• Use of concomitant medications that might interfere with the study evaluation;
• Pre-implantation genetic diagnosis/screening