Arguments for elective single-embryo transfer

Over the past 25 years, artificial reproductive techniques have significantly improved and are now a well-established practice. While pregnancy, without consideration of obstetric and neonatal outcomes, was the main focus of the practice in the past, today a practice is esteemed successful if a healthy baby is delivered in a short treatment time with low risks for the patient and the baby. Human reproduction itself is quite inefficient. During the period of conception, implantation and placentation to the delivery of a baby, a number of aberrations can occur, resulting either in no pregnancy or a loss of pregnancy. In order to compensate for the low implantation rate of human embryos, it is routine to transfer more than one embryo in each treatment cycle as a routine procedure. As a result, the incidence of multiple pregnancy (MP; twins and higher order pregnancies) after IVF/intracytoplasmic sperm injection is much higher (30%) than after natural conception (1%). The obstetric, neonatal and long-term consequences for the health of these children need to be scrutinized and financial costs incurred are relatively high. In order to reduce the incidence of MP, particularly in women with a high-risk profile, an elective single-embryo transfer (eSET) after selection of the embryo with the highest development potential becomes a preferred procedure in many countries (particularly European) in situations in which more than one good-quality embryo is available. Clinical trials have shown that programs with over 50% of eSET maintain high overall ongoing pregnancy rates (30% per started cycle) while reducing the MP rate to less than 10%. However, there is still no consensus regarding the subgroup of patients eligible for eSET, while the need to reduce MP is consensus among most expect.