Elective single-embryo transfer (SET), combined with subsequent transfer of frozen/thawed embryos, can maintain a high pregnancy rate with a dramatic decrease in multiple pregnancy rates. It has been argued that in the near future, SET should be the default policy for good-prognosis in vitro fertilization (IVF)/intracytoplasmic sperm injection (ICSI) patients. An alternative to elective SET is the use of natural-cycle IVF/ICSI. Although this approach has its attractive sides (easy, cheap, repeatable, and no ovarian hyperstimulation syndrome), its efficacy per cycle is low. The strength of elective SET resides in the fact that ovarian stimulation allows selection of the putative most competent embryo. The impact of SET will depend on the size of the group in whom it is applied. If criteria are very strict, the impact will be small, but the overall pregnancy rate is likely not to decrease. Clinical judgments regarding SET differ between centers and countries.

This chapter presents suggested options for the elimination of multiple pregnancies including selective fetal reduction, single blastocyst transfer and elective single-embryo transfer (eSET). Selective fetal reduction carries a risk of miscarriage and poses serious ethical and legal questions. Three trials comparing eSET with elective double embryo transfer (DET) were identified. All involved women who had undergone embryo transfer in a fresh in vitro fertilisation (IVF)/intracytoplasmic sperm injection (ICSI) cycle. It is clear that in a selected population the cumulative outcome of eSET is comparable with that of DET while virtually eliminating multiple pregnancies. The outcome of an eSET policy can be substantially enhanced in conjunction with an efficient and reliable embryo cryopreservation programme. Twin pregnancies resulting from IVF treatment are associated with higher maternal and perinatal morbidity. More data from pragmatic trials are to demonstrate whether a policy of eSET is effective, acceptable and financially viable in other clinical settings.