biostudies-literatureUnknown39(8)Youngster M<h4>Purpose</h4>To investigate the association between endometrial compaction and pregnancy rates in unstimulated natural cycle frozen embryo transfers.<h4>Design</h4>A single-center prospective cohort study. Endometrial thickness by transvaginal ultrasound and blood progesterone levels on the day of ovulation and the day of embryo transfer were evaluated in patients undergoing natural cycle frozen embryo transfer. Compaction was defined as > 5% decrease in endometrial thickness between ovulation day and day of transfer. Clinical and ongoing pregnancy rates in cycles with and without compaction were compared.<h4>Results</h4>Seventy-one women were included, of which 44% had endometrial compaction, with similar rates when subdividing the patients by day of transfer (day 3 or day 5). ClinicalJournal of assisted reproduction and genetics1909-1916https://www.ebi.ac.uk/biostudies/studies/S-EPMC9428085biostudies-literatureEndometrial compaction is associated with increased clinical and ongoing pregnancy rates in unstimulated natural cycle frozen embryo transfers: a prospective cohort study.PMC9428085Youngster MYerushalmi GBarkat JHourvitz AGat IGidoni YMor MBaruchin ORevel AAvraham SKedem AfalseEndometrial compaction is associated with increased clinical and ongoing pregnancy rates in unstimulated natural cycle frozen embryo transfers: a prospective cohort study.<h4>Purpose</h4>To investigate the association between endometrial compaction and pregnancy rates in unstimulated natural cycle frozen embryo transfers.<h4>Design</h4>A single-center prospective cohort study. Endometrial thickness by transvaginal ultrasound and blood progesterone levels on the day of ovulation and the day of embryo transfer were evaluated in patients undergoing natural cycle frozen embryo transfer. Compaction was defined as > 5% decrease in endometrial thickness between ovulation day and day of transfer. Clinical and ongoing pregnancy rates in cycles with and without compaction were compared.<h4>Results</h4>Seventy-one women were included, of which 44% had endometrial compaction, with similar rates when subdividing the patients by day of transfer (day 3 or day 5). Clinical2022-01-01T00:00:00Z2022 Aug2025-04-04T20:07:07.726Z2025-04-04T20:07:07.726ZS-EPMC94280853572742310.1007/s10815-022-02544-7