Endometrial compaction (decreased thickness) in response to progesterone results in optimal pregnancy outcome in frozen-thawed embryo transfers

Patients whose endometrium compacted (became thinner) after the administration of progesterone had a significantly higher ongoing pregnancy rate after frozen- thawed embryo transfer compared with patients whose endometrium did not change or became thicker.

Volume 112, Issue 3, Pages 503–509.e1


Jigal Haas, M.D., Ramsey Smith, B.Sc., Eran Zilberberg, M.D., Dan Nayot, M.D., James Meriano, M.Sc., Eran Barzilay, Ph.D., M.D., Robert F. Casper, M.D.



To evaluate whether the change in endometrial thickness between the end of the estrogen phase and the day of embryo transfer has an impact on the pregnancy rate in frozen-thawed embryo transfer (FET) cycles.


Retrospective observational cohort study.


Single tertiary care medical center.


Ultrasound images in 274 FET cycles were reviewed. All patients underwent endometrial preparation with the use of hormonal therapy.


Ultrasound measurements of endometrial thickness at the end of the estrogen phase and the day of embryo transfer.

Main Outcome Measure(s)

The change in endometrial thickness and ongoing pregnancy rate.


We calculated the ongoing pregnancy rate in patients whose endometrial thickness decreased (compacted) after starting progesterone by 5%, 10%, 15%, or 20% compared with patients with no change or increased endometrial thickness. The ongoing pregnancy rate was significantly increased at all levels of compaction compared with no compaction. The ongoing pregnancy rate showed a significant increase with each decreasing quartile of change in thickness (increased percentage of compaction) in the progesterone phase compared with the estrogen phase.


There is a highly significant inverse correlation between the ongoing pregnancy rate and the change of endometrial thickness between the end of estrogen administration and the day of embryo transfer.

Read the full text here.

Please sign in or register for FREE

Your Fertility and Sterility Dialog login information is not the same as your ASRM or EES credentials. Users must create a separate account to comment or interact on the Dialog.

Go to the profile of Alexander Quaas
about 3 years ago

This study introduces the very interesting concept of endometrial compaction and its influence on embryo transfer success to our field. The findings are very exciting, but there are a lot of open questions. Does the degree of compaction vary from cycle to cycle in the same patient? Is compaction truly a marker for endometrial receptivity? Is it worth canceling a cycle, as the authors suggest, if the endometrial thickness does not decrease from the lining check to the day of the transfer?

The results are impressive, but the ROC curve with the area under the curve of 0.684 puts into question whether endometrial compaction is ready as a diagnostic or prognostic test.

From a clinical perspective, clinicians may start measuring endometrial thickness routinely on the day of transfer, and assess their own success rates based on compaction data. From a research perspective, what kind of translational / clinical trials are needed to further support the findings from this study?

Go to the profile of MŠn Alyah
over 2 years ago

How can I participate in achieving endometrial compaction to improve pregnancy results in FET ??