This study aims to assess the clinical significance of cleavage stage (Day 3) assisted hatching compared to assisted hatching at the blastocyst stage (Day 5,6,7) of embryo development at the time of trophectoderm (TE) biopsy for patients undergoing in vitro fertilization (IVF) and preimplantation genetic testing for aneuploidy (PGT-A) for treatment of their infertility.

The proposed study aims to perform a split cohort study where each patient's cohort of fertilized zygotes, (two pronuclei or 2PNs) is split into two groups and randomized, thus allowing each patient to serve as their own control and decreasing confounding variables. Half of the cohort will proceed with the current standard of day 3 or cleavage assisted hatching and the other half of the cohort will receive the sequential hatching and trophectoderm biopsy procedure at the blastocyst stage of embryo development.

Inclusion Criteria for participants:

1. Patients undergoing an IVF cycle with plan for subsequent FET of a single euploid embryo

2. <4 2PNs prior to randomization

3. Female partners age <42 years old at start of VOR cycle

4. Normal ovarian reserve:

   1. AMH ≥ 1.2 ng/mL
   2. AFC ≥ 8
   3. FSH ≤ 12IU/L

5. BMI <38

6. Patients who desire to transfer the best quality embryo for their embryo transfer.

Exclusion Criteria for participants:

1. All patients who do not voluntarily give their written consent for participation
2. Patients with a prior failed IVF cycle - defined as no blastocysts
3. Patients with a history of more than one failed euploid embryo transfer
4. Donor oocyte cycles
5. Gestational Carriers
6. Male partner with <100,000 total motile spermatozoa per ejaculate (donor sperm is acceptable)
7. Use of surgical procedures to obtain sperm
8. Communicating hydrosalpinges without a plan for surgical correct prior to frozen embryo transfer
9. Endometrial Insufficiency, as defined by a prior cycle with maximal endometrial thickness <6mm,), or persistent endometrial fluid
10. Single gene disorders, chromosomal translocations, or any other disorders requiring a more detailed embryo genetic analysis than standard PGT-A