Patient-specific predictors of successful frozen embryo transfer using the freeze-all protocol: a retrospective...

The aim of this study was to examine various patient factors affecting first programmed embryo transfer (ET) outcomes under the freeze-all policy at a single tertiary university infertility center.

This retrospective observational study reviewed the medical records of 243 couples who underwent their first ET using blastocysts collected under the freeze-all antagonist-controlled ovarian stimulation (COS) protocol from 2015 to 2023. Patients were grouped into pregnant and nonpregnant groups, and their data, including demographics, COS and ET outcomes, and embryo storage duration, were analyzed.

Patient body mass index, cause of infertility, follicle-to-oocyte index, distribution of blastocyst grades, number of transferred embryos, and embryo storage duration were not significantly different between the groups. In a simple comparative analysis, patients with successful clinical pregnancy tended to have significantly lower female and male age (33.83±3.67 and 35.32±4.54 years vs. 37.07±4.15 and 39.33±5.60 years, respectively), higher anti-Müllerian hormone levels (6.27±5.32 ng/mL vs. 4.14±3.82 ng/mL) and antral follicle counts (14.20±8.26 vs. 10.04±5.75), and higher numbers of retrieved oocytes and metaphase II oocytes (13.74±6.92 and 9.64±6.19 vs. 11.21±6.04 and 7.53±5.56, respectively). Multivariate logistic regression analysis of these variables revealed that only male age was a significant factor for successful clinical pregnancy (odds ratio, 4.768; 95% confidence interval, 1.252-18.162; p=0.022).

During the first programmed ET using blastocysts collected under the freeze-all antagonist COS protocol, male age and correspondingly the quality of gametes for fertilization were crucial for successful pregnancy, having more importance than calculated female ovarian reserve and embryo storage duration.