Endometrial compaction is associated with increased clinical and ongoing pregnancy rates in unstimulated natural cycle frozen embryo transfers: a prospective cohort study.

Purpose To investigate the association between endometrial compaction and pregnancy rates in unstimulated natural cycle frozen embryo transfers. Design 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.

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). Clinical and ongoing pregnancy rates were higher in the compaction group compared to the non-compaction group (0.58 vs. 0.16, P < 0.001; 0.52 vs. 0.13, P 10% and > 15% revealed similar pregnancy rates as > 5%, with no added benefit to higher degrees of compaction.

About half the patients in our study undergoing unstimulated natural cycle frozen embryo transfer experienced compaction of the endometrium, occurring as early as day 3 post-ovulation. This was significantly correlated with increased clinical and ongoing pregnancy rates. Similar content being viewed by others

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H., and S.A. drafted the first version of the manuscript. M. Y., A. H., and S. A. contributed to data analysis and interpretation. All authors revised the manuscript and approved the final submitted version. Corresponding author Ethics declarations Conflict of interest The authors declare no competing interests. Additional information Publisher's Note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. Supplementary Information Below is the link to the electronic supplementary material. Rights and permissions About this article Cite this article Youngster, M., Mor, M., Kedem, A. et al. Endometrial compaction is associated with increased clinical and ongoing pregnancy rates in unstimulated natural cycle frozen embryo transfers: a prospective cohort study. J Assist Reprod Genet 39, 1909–1916 (2022). https://doi.org/10.1007/s10815-022-02544-7 Received: Accepted: Published: Version of record: Issue date: DOI: https://doi.org/10.1007/s10815-022-02544-7