The Role of hCG in Thawed Embryo Transfer

Inclusion Criteria: 1. Female adult expecting to receive transfer of a thawed embryo. 2. At least one available frozen blastocyst of transferrable quality. 3. Non-menopausal female with at least one antral follicle. 4. Use of pre-implantation genetic testing (PGT), embryos derived from donor oocytes and/or donor sperm, a gestational carrier, and history of prior transfer(s) regardless of outcome are allowed. 5. Subsequent embryo transfers after failed transfers under this study are allowed, but not after a transfer that has resulted in ongoing pregnancy at ten weeks gestation under this study. Exclusion Criteria: 1. Minors (age\<18 years). 2. Use of embryo(s) frozen at another center. 3. Patient insistent on transfer of two embryos. 4. Patient or partner unable to provide informed consent in English. 5. Patient already enrolled in any other research study for her embryo transfer. 6. History of anti-phospholipid syndrome or any other indication for use of Lovenox in pregnancy. 7. Patient for whom the physician assesses this protocol is inappropriate or unsafe.