Endometrial compaction did not predict ongoing pregnancy after modified natural-cycle FET

In a prospective multicentre cohort of 207 patients undergoing single euploid blastocyst transfer in modified natural-cycle frozen embryo transfer, endometrial compaction was not associated with ongoing pregnancy. The findings do not support compaction as a predictor of reproductive outcomes in this setting.

Cohort included 207 single euploid blastocyst transfers.
Compaction was not associated with ongoing pregnancy.
Results were consistent across alternative compaction thresholds.
Uneven group sizes may have reduced statistical power.

A prospective observational cohort study at six assisted reproduction units in Spain assessed whether endometrial compaction predicts ongoing pregnancy after modified natural-cycle frozen embryo transfer (mNC-FET). It included 207 women aged 18–50 years who received a single euploid blastocyst. Endometrial thickness was measured by transvaginal ultrasound on the day of ovulation triggering and on the day of embryo transfer. Compaction was defined as a reduction of at least 5%; ongoing pregnancy was foetal cardiac activity at 10 weeks.

Fifty-eight patients (28.0%) met the compaction threshold. Ongoing pregnancy occurred in 50.0% of this group and 53.7% of those without compaction (P=0.633). After adjustment for age, previous live births and miscarriages, BMI, and oocyte origin, the association remained nonsignificant (adjusted odds ratio 0.80, 95% CI 0.38–1.67). Results were also nonsignificant using compaction thresholds of 10% and 15%, and for the reported secondary reproductive outcomes.

The findings do not support endometrial compaction as a predictor of ongoing pregnancy in mNC-FET with euploid embryos. Interpretation is limited by the uneven group sizes, some externally obtained trigger-day measurements, and incomplete live-birth data. The study was observational and does not establish whether ultrasound measurements could be useful in other transfer protocols or populations.

In practice

For patients undergoing modified natural-cycle frozen embryo transfer with a single euploid blastocyst, this cohort found that a 5% or greater reduction in endometrial thickness between ovulation triggering and transfer did not identify those more likely to have an ongoing pregnancy. The result also held for higher compaction thresholds. These observational findings do not establish that compaction has no predictive value in other protocols or populations; group sizes were uneven, and live-birth data were incomplete. The study does not support using compaction as a pregnancy predictor in this specific setting.

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Source

Human Reproduction: Endometrial compaction and ongoing pregnancy in modified natural cycle frozen euploid embryo transfer: a prospective multicentre cohort study with standardized transvaginal ultrasound assessment ↗

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