Embryo implantation is a crucial event in the establishment of a pregnancy. Although the clinical and culture conditions to obtain a "good quality" embryo are well advanced today, endometrial receptivity remains a major barrier in assisted reproductive techniques. Once a high-quality embryo is transferred, impaired uterine receptivity is believed to be one of the major reasons behind failure of the establishment of pregnancy.

Inclusion Criteria:

• Women between the ages of 18 to 40 inclusive at the time of oocyte retrieval
• Prescription of a single frozen embryo transfer - substituted cycle protocol
• Participant has at least 2 vitrified good quality blastocysts

Exclusion Criteria:

• Women undergoing fertility preservation
• Stage IV severe endometriosis
• Severe malformation, adenomyosis or uterine anomaly including fibroids deforming the uterine cavity ≥ 5 cm
• Positive results of screening for either participant or partner for HIV antibodies, Hepatitis B (other than surface antibodies present after vaccination) or Hepatitis C