The Effectiveness of Two Cycles of Single Embryo Transfer (Fresh + Frozen) vs. One Fresh Double Embryo Transfer in Women Treated in an Oocyte Donation Program

Introduction: The benefits of two Single Embryo-Transfer (SET) cycles (transferring of a single fresh embryo and a second, single frozen-thawed embryo transfer in another cycle), as compared to fresh Double Embryo-Transfer (DET) in autologous IVF treatment, are known. However, in oocyte donation treatments the endometrial milieu differs by avoiding the high estradiol levels used in autologous cycles, which can impact the endometrium. A comparison between SET and DET may provide insight into the different outcomes of fresh embryo transfer vs. frozen thawed embryo transfer.Materials and methods: A retrospective cohort study conducted at two IVF units from 2010-2019. Patients in the oocyte donation program were divided into 2 groups: Group A – DET: two fresh embryos were transferred in one cycle; Group B – SET: a single fresh embryo was transferred in one cycle, and in a subsequent cycle a second, single, frozen-thawed embryo was transferred. Implantation rate, multiple pregnancy rate and preterm birth rate were compared between the two groups.Results: Two hundred forty-three women met the inclusion criteria; 168 women comprised the DET group and 75 women the SET group. The two groups were similar in demographic and clinical characteristics. Implantation rates were comparable in the SET and DET groups (32.0% and 39.3%, respectively; p=0.15). The multiple pregnancy rate was significantly higher in the DET group (37.5% vs. 0%; p<0.001), as was the rate of preterm birth ( 45.6% vs. 22.6%, p=0.03). Conclusion: Implantation-rate and live birth rate in two SET cycles are comparable to DET in egg donation IVF treatment cycles. However, multiple and preterm pregnancies in single embryo transfer group were significantly reduced.