Endometrial compaction does not predict live birth rate in single euploid frozen embryo transfer cycles

Purpose To evaluate whether endometrial compaction using sequential transvaginal ultrasound is associated with improved live birth rates in medicated single euploid frozen embryo transfer (FET) cycles. Methods Prospective observational cohort study at a private fertility clinic. Patients who underwent FETs between January and December 2018 were assessed for inclusion. The change in endometrial thickness between the end of the estrogen phase and the day before embryo transfer, measured by sequential transvaginal ultrasound, was used to categorize cycles with compaction (≥ 5%), no change, or expansion (≥ 5%). FET cycle outcomes were then compared between groups. The primary outcome was live birth. Secondary outcomes include clinical pregnancy rate and rate of spontaneous abortion. Results Of the 259 single euploid medicated FETs performed during the study period, only 43/259 (16.6%) of the cycles demonstrated ≥ 5% compaction, whereas 152/259 (58.7%) expanded and 64/259 (24.7%) were unchanged. Live birth rates did not differ between cycles with compaction (58.1%), no change (54.7%), or expansion (58.6%), p = 0.96. Clinical pregnancy and spontaneous abortion rates were also similar between groups. Conclusion The vast majority of cycles did not demonstrate endometrial compaction. Endometrial compaction is not associated with live birth rate or spontaneous abortion rate in medicated single euploid FETs in this cohort.