Impact of elective-Single Embryo Transfer at the cleavage stage on live birth and multiple pregnancy rates

Multiple birth is the single biggest risk to the health and welfare of children born after in vitro fertilisation (IVF). The transfer of two embryos after IVF treatment leads to a high probability of twin pregnancies and high risk of complications for both the mother and the child.The main risk to the fetus is prematurity, which is responsible for the high perinatal mortality and morbidity as well as the increased incidence of long-term neurological complications. The considerable emotional impact of the adverse effects of prematurity is also an issue for the parents. Henceforth, it is very important to identify possible ways of preventing this serious complication of IVF. The elective transfer of only one embryo has been suggested as a way forward, however applying a blanket elective-Single Embryo Transfer (e-SET) policy to all IVF cycles is inappropriate as this will disadvantage some patients by reducing significantly their probability of live birth. It has recently been shown that e-SET of embryos at the cleavage stage reduces the chance of live birth by 38% and that of multiple pregnancy by 94% (Fertil Steril 2010; 94:936-45). Increasing the number of e-SET attempts (fresh and/or frozen) may result in a cumulative live birth rate similar to that of DET. Individualisation and careful selection using criteria such as the woman's age and the embryo quality is crucial to maintain acceptable pregnancy outcomes.