Elective single-embryo transfer

N umerous publications have investigated the practice of elective single-embryo transfer (eSET) (1–27). Single-embryo transfer after in vitro fertilization (IVF) has been advocated as the only effective means to avoid multiple pregnancy in IVF cycles (28). Elective SET is defined as the transfer of a single embryo at either the cleavage or blastocyst stage of embryo development that is selected from a larger number of available embryos. It is defined in the Society for Assisted Reproductive Technologies (SART) reporting guidelines as ‘‘an embryo transfer in which more than one high-quality embryo exists but it was decided to transfer only one embryo.’’ Historically, to compensate for low rates of implantation for individual embryos and achieve ‘‘acceptable’’ pregnancy rates, multiple embryos have been transferred to the majority of IVF patients. Consequently, IVF carries a high risk of multiple pregnancy and its associated adverse effects on mothers and children, as detailed in the ASRM Practice Committee Document titled, Multiple gestation associated with infertility therapy (29). However, as implantation rates (IRs) have improved, the practice of transfering multiple embryos must be reassessed. There are many issues that