ABSTRACT
In this chapter, the experience to date with elective single-embryo transfer is described in four European countries, in two of which (Finland and Belgium) the idea was pioneered, and in two of which (Sweden and The Netherlands) the in vitro fertilization (IVF) community was quick to follow. It is clear that others also have taken the way of elective single-embryo transfer. A Slovenian group has published a retrospective randomized trial comparing the transfer of one or two day-2 versus one or two day-5 embryos obtained after IVF/intracytoplasmic sperm injection (ICSI)1. They did not find a difference between day-2 versus day-5 transfers but failed to mention the results in the subsets of patients receiving only one embryo (n=62 for day-2 and n=46 for day-5 single-embryo transfers). A Spanish group reported their experience with the transfer of one versus two embryos, showing a pregnancy rate of 42.2% with elective single-embryo transfer versus 68.6% for elective double-embryo transfer with 54.2% twins2. An Australian group compared elective single-embryo transfer on day 5 with twoembryo transfer on day 5 and did not find a diminished live birth rate3. The live birth rate per embryo was 36% in both groups; however, the twinning rate was 50% in the double-embryo transfer group. Using frozen-thawed embryos the cumulative pregnancy rate was 60% for both groups. Other centers have initial experience with elective single-embryo transfer confirming ongoing pregnancy rates of around 35%.
