Higher blastocyst implantation in frozen versus fresh embryo transfers in good prognosis patients

There is emerging evidence that frozen embryo transfers provide a more favorable environment for implantation as compared to fresh embryo transfers. Our objective was to determine if there is a clinical benefit to frozen versus fresh blastocyst transfers in good prognosis patients.Subjects undergoing their first or second IVF/ICSI cycle <38 years of age in an OCP pretreated GnRH antagonist stimulation protocol with supernumerary embryos available for blastocyst cryopreservation were eligible for analysis. Primary transfer was exclusively blastocyst transfer. Exclusion criteria consisted of rescue ICSI, preimplantation genetic testing, donor oocytes, and surrogacy. The cohort was divided into two groups based on whether they underwent a fresh vs. frozen primary transfer. The implantation rates were compared using mixed-effects logistic regression. The clinical pregnancy and live birth rates were compared using logistic regression adjusted for number of oocytes retrieved and number of embryos transferred. All models included age, reason for treatment, and number of prior births as covariates.A total of 615 subjects were included in the study. There were no differences in the two groups with respect to age, BMI, baseline ovarian reserve testing, total gonadotropin dosage, and duration of stimulation. The implantation rate was higher in the frozen-embryo group as compared to the fresh-embryo group (59% and 48% respectively; OR 1.58; 95% CI 1.02-2.44). There was a trend towards higher clinical pregnancy and live birth rates in the frozen-embryo group. These differences persisted in the adjusted analysis.Among good prognosis patients undergoing IVF, frozen embryo transfer was associated with improved implantation rates. Consideration should be given to primary frozen blastocyst transfer in this population.