Subcutaneous Progesterone in Frozen- Thawed Single Euploid Blastocyst Transfer.

This is a multicenter, randomized, double-blind, double-dummy, active-controlled, non-inferiority clinical study in women aged 35 to 42 years. This study will investigate the safety and efficacy of Progesterone-IBSA to support euploid embryo blastocyst implantation and early pregnancy after frozen embryo transfer (FET) in a modified natural cycle as a treatment for infertile women. Subjects will be randomized to receive either active Progesterone-IBSA or Crinone 8% for luteal and early pregnancy support and these two groups will be compared.

Inclusion Criteria: * subject has given written informed consent; * Premenopausal women 35 to 42 years of age at the time of consent (at least 35 \[including day of birthday\] and no more than 42 \[up to the day before their 43rd birthday\]); * Valid indication for IVF treatment (i.e. history of infertility according to ASRM definition, single women or same-sex couples); * Consistent, regular spontaneous ovulatory menstrual cycle with normal length (24-38 days included); * Body mass index (BMI) \< 38 kg/m2; * Subject with at least one euploid frozen blastocyst from a previous IVF treatment cycle; * Less than 3 previous consecutive euploid blastocyst transfers without a life birth; * Baseline Follicle Stimulating Hormone (FSH) \< 15 mIU/mL, and Anti Muellerian Hormone (AMH) \>0.7 ng/mL (within 6 months from screening for subjects requiring a stimulation cycle to obtain a euploid embryo); and Estradiol (E2) \< 90 pg/mL and Progesterone (P4)\< 1.5 ng/mL at Visit 1 (for all subjects); * Semen used during IVF(for subjects requiring a stimulation cycle to obtain a euploid embryo) was produced by ejaculation (not surgically derived sperm) from either the partner or from a sperm donor. Donor must be 18-40 years of age at the time of collection and compliant with 21 Code of Regulations (CFR) section 1271 Subpart C; * Hysterosalpingography, hysteroscopy, 3D ultrasound or sonohysterogram documenting a normal uterine cavity within the last year; * Normal cervical cytology/High Risk human papillomavirus (HPV) testing per American College of Obstetricians and Gynecologists guidelines. Exclusion Criteria: * Oligo or anovulation (spontaneous menses \> 39 days apart); * Breastfeeding or Pregnancy; * Contraindication to pregnancy (i.e. an active, uncontrolled clinically significant medical condition or abnormality of the sexual organs determined by the provider); * Known family history of major congenital anomalies; * Moderate to severe current endometriosis (stage 3 or 4); * Presence of a unilateral or bilateral hydrosalpinx that communicates with the uterus, that has not been ligated prior to treatment; * Recurrent pregnancy loss (RPL) as defined by the American Society of Reproductive Medicine (ASRM) as two or more consecutive failed clinical pregnancies; * Presence of a submucosal or intramural fibroid \> 4 cm which distorts the uterine cavity or are \> 5 cm in diameter; * Untreated uterine pathology that could impair embryo implantation (i.e. scarring/Asherman's syndrome or intra uterine polyps \> 1 cm in size); * Type 1 or 2 diabetes mellitus based on American Diabetes Association (ADA) criteria3; * Uncontrolled adrenal or thyroid dysfunction; * History of conditions (i.e. toxic shock syndrome) that would contraindicate use of a vaginal progesterone product; * Subjects with hepatic impairment (liver function tests \> 2x upper limit of normal); * Subjects with renal impairment (estimated creatinine clearance \