Is it possible to plan for a day 7 blastocyst (embryo that has developed for 7 days) transfer?

Day 7 Blastocyst Transfer: Feasibility and Outcomes

Yes, day 7 blastocyst transfer is technically feasible and can result in live births, but these embryos have significantly lower reproductive potential compared to day 5 or day 6 blastocysts, with clinical pregnancy rates of 16.7-52.6% and live birth rates of 21.5-46% for euploid embryos. 1

Viability of Day 7 Blastocysts

Day 7 blastocysts represent a small but viable subset of embryos that merit consideration for transfer:

• Day 7 embryos comprise less than 10% of usable embryos but demonstrate non-negligible pregnancy potential 1
• Successful live births have been documented with day 7 blastocyst transfers, including healthy twin deliveries after fresh day 7 transfer 2
• Extended culture to day 7 allows identification of viable embryos that would otherwise be discarded, providing additional transfer opportunities for select patients 3

Critical Limitations and Counseling Points

Reduced Developmental Potential

• Day 7 blastocysts have lower blastulation rates compared to day 5 and 6 embryos 1
• Aneuploidy rates are significantly higher in day 7 embryos (euploidy rate 35.9%) compared to day 5 (53.5%) and day 6 (40.4%) blastocysts 3
• Miscarriage rates are substantially elevated at 22.2% for day 7 embryos versus 2% for day 5/6 embryos 3

Pregnancy Outcomes

For euploid day 7 blastocysts specifically:

• Clinical pregnancy rates range from 16.7% to 52.6% across recent studies 1
• Live birth rates range from 21.5% to 46% for euploid day 7 embryos 1
• Implantation potential remains high (56.3-79.3%) for vitrified-warmed euploid day 7 blastocysts, though live birth rates are lower (43.8% vs. 67.4-77.2% for day 5/6) due to increased pregnancy loss 3

Practical Implementation Strategy

When to Consider Day 7 Transfer

Day 7 blastocyst transfer should be considered for:

• Patients with limited embryo availability where day 7 embryos represent the only transfer option 1
• Cycles using preimplantation genetic testing (PGT) where extended culture allows identification of additional euploid embryos 3
• Patients who have exhausted day 5 and day 6 embryo options and require additional transfer opportunities 1

Technical Considerations

• Trophectoderm biopsy should include 5-8 cells for PGT cycles, consistent with general PGT standards 4
• Vitrification is the preferred cryopreservation method for day 7 blastocysts, with frozen embryo transfer recommended 4
• Assisted hatching may be beneficial for day 7 embryos to facilitate more rapid endometrial contact 2

Mandatory Transfer Protocol

Single embryo transfer (SET) must be applied for day 7 blastocysts, regardless of their slower development or previous failed cycles:

• Transfer of more than two embryos is never recommended at the blastocyst stage 4
• The decision to perform double embryo transfer should not be based on the number of previous unsuccessful treatments, duration of infertility, or embryo quality 4
• SET should be practiced in vitrified-warmed blastocyst transfer cycles regardless of blastocyst quality, including day 7 embryos 4

Patient Counseling Framework

Patients considering day 7 blastocyst transfer must understand:

• Day 7 embryos have lower but non-zero reproductive potential compared to earlier-developing blastocysts 1
• Higher aneuploidy rates necessitate PGT consideration to optimize outcomes 3
• Increased miscarriage risk even with euploid day 7 embryos requires appropriate expectation setting 3
• Day 7 embryos represent an additional opportunity rather than an equivalent alternative to day 5/6 blastocysts 1