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