Frozen embryo replacement cycle :Two methods traditionally used: the spontaneous cycle and the artificial cycle.Now, Emergence of new protocols: NPP-FET or "Natural proliferative phase - frozen embryo transfer" Demonstrate non-inferiority between the NPP-FET and the spontaneous cycle, and superiority in terms of planning.

The protocol Natural proliferative phase/Natural Programmed by Progesterone, Patients with regular cycles, candidates for replacement of embryos frozen in a spontaneous cycle. The monitoring of the cycle is carried out by taking blood and follicular ultrasound between the 10th and 13th day of the cycle. Support luteal phase by intravaginal progesterone (utrogestan 200 mg) 1 tablet, 2 times per day, is initiated once the following criteria are met:

• Thickness of the endometrium > 7 mm on ultrasound
• Ovarian follicle > 14 mm
• Estradiol( E2) > 120 pg/mL Embryo transfer is scheduled on the 6th day of progesterone exposure exogenous. A progesterone dosage on the day of transfer will be systematically realized

Inclusion Criteria:

• Single transfer Blastocyste

Exclusion Criteria:

• PGT (Preimplantation genetic diagnosis)
• Testicular Sperm
• Donor oocytes

Patients with regular cycles, candidates for replacement of embryos frozen in spontaneous cycle

Patients with regular cycles, candidates for replacement of embryos frozen in spontaneous cycle