Embryo Transfer Timing After Egg Retrieval
Embryo transfer is typically performed either 2-3 days (cleavage stage) or 5-6 days (blastocyst stage) after egg retrieval in IVF/ICSI cycles.
Standard Transfer Timing Options
Cleavage Stage Transfer (Day 2-3)
- Day 2 transfer occurs 48 hours after egg retrieval 1, 2
- Day 3 transfer occurs 72 hours after egg retrieval 1, 3, 2
- These represent cleavage stage embryos that have undergone initial cell divisions 3, 4
Blastocyst Stage Transfer (Day 5-6)
- Day 5 transfer occurs 120 hours after egg retrieval 5, 2
- Day 6 transfer may also be performed at the blastocyst stage 2
- Blastocyst transfer provides better synchronization with the female reproductive tract 5
Clinical Decision-Making for Transfer Timing
The choice between cleavage stage and blastocyst transfer should be based on embryo quality and number, not assumed superiority of blastocysts. While blastocyst transfer has been traditionally viewed as higher quality, live birth rates are comparable between day 2, day 3, and day 5/6 transfers when controlling for confounding factors 2.
Key Considerations:
- Clinical pregnancy rates show a linear association with developmental stage (77.3% for day 2,87.5% for day 3, and 90.3% for days 5/6) 2
- However, live birth rates are comparable across all transfer stages when adjusted for maternal age and other factors 2
- Blastocyst transfer requires fewer embryos to be transferred compared to cleavage stage, particularly in women with excellent prognoses 3
Frozen Embryo Transfer Protocol
For frozen embryo transfer cycles using hormone replacement therapy:
- Progesterone initiation occurs after 12-14 days of estrogen priming 6
- Blastocyst transfer is scheduled 117-120 hours (approximately 5 days) after the first progesterone dose 6
Important Caveats
- Approximately 28-30% of embryos may arrest before reaching blastocyst stage, limiting the feasibility of day 5/6 transfer in some cases 5
- Maternal age has an independent effect on live birth rates regardless of transfer timing 2
- The decision should account for the number of available embryos and their quality at each developmental stage 3, 4