Endometrial Compaction in Response to Progesterone Administration and Good Endometrial Vascularity Improves the Clinical Pregnancy Rates in Hormone Replacement Frozen Embryo Transfers

Purpose: The current study assessed the effect of endometrial compaction and vascularity on clinical pregnancy rates (CPR) in women undergoing frozen embryo transfer (FET). Methods: Prospective observational study. Endometrial compaction and its vascularity were studied by transvaginal ultrasound (TVS) and evaluated CPR. Results: Out of 156 women, 81 had endometrial compaction, 64 had no change in the endometrium, and 11 had an increase in endometrial thickness (ET). Clinical pregnancy rate was 58% among those with endometrial compaction compared to 20.3% among those with no change in ET and 9.1% among those with an increase in ET on the day of FET (p-value < 0.001). Women with 5–10% endometrial compaction, CPR was 61.24%, those with 11–15% compaction had the highest pregnancy rate of 88.2%, and those with compaction of >15% had CPR of 66.6%. Endometrial compaction with zone 3 vascularity had a CPR of 64.2%, and those with zone 4 had 91.7% CPR compared to those with zone 2 vascularity (12.5%), p-value < 0.001. There was poor CPR in women with an increase in ET, though the endometrial vascularity was good. Conclusion: A significant increase in CPR was observed in women who had endometrial compaction with good vascularity of the endometrium, unlike those with poor vascularity. Women with no change or increase in ET had poor pregnancy rates. Hence, assessing the endometrium on the day of starting progesterone and on the day of embryo transfer is essential. If the endometrial compaction has not occurred and/or the endometrial vascularity is poor, the cycle should be considered for cancellation. Clinical significance: Endometrial compaction and good endometrial vascularity are essential for embryo implantation in FET cycles.