The embryo transfer, i.e. the placement of in vitro fertilized ova into the woman’s uterus, is usually performed at the 2^nd or the 3^rd day after the egg collection. In some instances, embryo transfer may be performed at the 5^th or 6^th day (at the embryonic stage of blastocysts). The woman comes to the Unit at the time agreed, with no need of not having eaten (once she won’t be administered any anesthesia); and the embryo transfer is performed under a simple process (not more painful than a Pap smear test): the embryo(s) graded as the ‘best’ (considering specific morphological criteria) is/are chosen among the available embryos; it/they are then placed in a special syringe containing a small quantity of culture fluid, and through an extra thin catheter inserted by the physician via the cervix is/are transferred into the uterine cavity. The woman stays in bed for a while and then is able to leave the Unit. The number of embryos transferred each time is determined by factors like the woman’s age and the quality of available embryos, and is further restricted to avoid multiple pregnancies (as those are the main cause of premature labors with all subsequent negative effects). According to the official instructions given by the Greek Human Fertilization and Embryology Authority, this number should not exceed 3 embryos for women aged up to 40 years, and 4 embryos for women aged over 40.