A comparative study to determine whether bed rest after embryo transfer (ET) affects on IVF (In Vitro Fertilization)outcome. This study includes 240 patients undergoing IVF treatment with donated oocytes. All the procedures of IVF, of the embryo transfer, and of the administration of medications are performed as always and there are no variations. The only highlighted procedure in this study is immediately after the embryo transfer. There are two groups: one which will rest in bed for 10 minutes after the transfer and one which will not rest after the transfer. Both procedures are common, usually depending on the habitual clinical practice of each clinic internationally. Patients from both group receive the routine post transfer instructions and treatment.