Multiple pregnancy--the evidence for single-embryo transfer.

With the introduction of numerous new technologies, human reproduction has undergone considerable development during the last 25 years. The possibilities for treating both female and male infertility are today less of a medico-technical and more of a socio-economic problem. The high incidence of multiple pregnancy is the problem that causes most concern, with impact upon the infertile couple, offspring and society. Attempts to solve this problem have been made but more work is needed.