Clarification: ET Refers to Endometrial Thickness, Not Embryo Size
An endometrial thickness (ET) of 8.6 mm is acceptable for embryo transfer and falls within the normal range for successful implantation. While the provided guidelines focus primarily on the number of embryos to transfer rather than endometrial thickness criteria, this measurement is generally considered adequate for proceeding with transfer.
Understanding the Question
Your question appears to ask about endometrial thickness (ET = 8.6 mm), not embryo size. The guidelines provided do not establish specific endometrial thickness cutoffs as contraindications to embryo transfer 1.
Key Points About Endometrial Thickness
ESHRE guidelines explicitly state that endometrial characteristics should not determine whether to proceed with embryo transfer in frozen embryo transfer cycles 2, 3
The focus of current guidelines is on preventing multiple pregnancy complications rather than establishing rigid endometrial thickness criteria 2
An endometrial thickness of 8.6 mm is within the range typically considered adequate for embryo transfer in clinical practice
Critical Embryo Transfer Recommendations
Regardless of endometrial thickness, the following evidence-based recommendations apply:
Single embryo transfer (SET) should be applied in vitrified-warmed blastocyst transfer cycles regardless of embryo quality 1, 4
For donor embryo transfers, only elective single embryo transfer (eSET) must be practiced with no exceptions 2, 3
The decision to transfer multiple embryos should never be based on previous unsuccessful treatments, duration of infertility, or previous pregnancy history 1
Common Pitfalls to Avoid
Do not delay transfer based solely on endometrial thickness measurements in the 8-9 mm range, as guidelines do not support this practice 2
Do not assume that transferring multiple embryos will compensate for perceived endometrial inadequacy—this significantly increases multiple pregnancy risks with a 30-fold higher multiple pregnancy rate compared to repeated SET 2, 3
Ensure proper embryo transfer technique with soft catheters, gentle manipulation, and ultrasound guidance to optimize outcomes 5, 6