ABSTRACT
The efficiency of in vitro fertilization (IVF) and embryo transfer (ET) in the human is low, with fewer than 30% of embryos that are transferred ever realizing full developmental potential.1 Since implantation rates have remained relatively low, there has been a practice of replacing multiple embryos (2-6) in order to increase the likelihood of a pregnancy. This has led to an unacceptable level of high-order multiple pregnancies. To overcome this problem, some countries have mandated the number of embryos that can be replaced, in some instances limiting this number to one in certain age groups. Although this will reduce the level of multiple pregnancies it can also reduce pregnancy rates, since there are data showing that the number of embryos replaced affects the pregnancy rate. What is required is a reliable way of selecting embryos that have the most potential for implantation, thus reducing the number of embryos needed without compromising the patient.
