Fresh vs. frozen: pregnancy outcomes and treatment efficacy between fresh embryo transfer vs. untested freeze-all cycles

To compare pregnancy outcomes after single blastocyst embryo transfer among patients whose first autologous embryo transfer was either a fresh embryo transfer or a frozen embryo transfer (FET) after a freeze-all, in the absence of preimplantation genetic testing for aneuploidy (PGT-A). A multicenter retrospective cohort analysis. National multicenter fertility practice. A total of 8,319 autologous first blastocyst embryo transfers in the absence of PGT-A were analyzed. Of them, 6,755 transfers were fresh embryo transfer (ET) and 1,564 transfers were FET after freeze-all. Patients underwent either a fresh or a frozen initial autologous, single blastocyst transfer in the absence of PGT-A. Primary outcome measure was live birth rate. Secondary outcome measures included positive pregnancy test, clinical pregnancy rate, and miscarriage rate. Live birth rate was comparable between the fresh ET and FET groups in the absence of PGT-A, after performing generalized estimating equation modeling to account for age, body mass index, antral follicle count, basal follicle-stimulating hormone, progesterone on day of trigger/day of final lining check, peak estradiol during in vitro fertilization stimulation cycle, number of oocytes retrieved during ovarian stimulation cycle, and primary diagnosis. Similarly, the secondary outcome variables of positive pregnancy test, clinical pregnancy rate, and miscarriage rates were comparable between the cohorts. These findings were observed in the entire study group, within each age category of 40 and among each stratified peak estradiol group. In the absence of PGT-A, patients and fertility providers can elect to pursue either fresh ET or embryo freeze-all with subsequent FET during the first autologous in vitro fertilization cycle.