How many embryos should be transferred in in vitro fertilization and tubal embryo transfer?

In order to achieve higher pregnancy rates, more than one embryo is usually transferred in in vitro fertilization (IVF) programs. Tubal embryo transfer (TET) produces an even higher pregnancy rate. However, the number of embryos that should be transferred in TET programs remains to be clarified. We studied a series of 241 consecutive TET cycles and analyzed their clinical characteristics, embryo numbers, cumulative embryo score (CES), and pregnancy outcomes. The results demonstrated that 1) four embryos was an adequate number to obtain a satisfactory pregnancy rate and fewer multiple pregnancies, 2) older patients and cases with male factor had less chance of pregnancy and more than four embryos could be transferred, and 3) CES values >40 were preferred, but for young patients with unusually high anxiety about multiple pregnancies, a CES of 21 to 40 was optimal. A policy of transfer that limits transfer to a maximum of two, three or four embryos is not suitable in all cases and other factors (eg. repeated IVF failure or older age) should be individually considered. Therefore, two equations utilizing CES, age and failure of previous TET as the factors were developed to help practitioners to evaluate how many embryos should be transferred on an individual basis.