Genomic Tool Selects Most Suitable Eggs for IVF

Genetic markers have been identified that allow the selection of eggs with the best chance of leading to successful pregnancy after in-vitro fertilization (IVF). This could both increase the success rate of single embryo transfer and diminish the risk of multiple pregnancies.

Currently, assessment of embryos that are to be transferred into a woman's uterus is based on visible criteria such as appearance and division rate. At least 30% of embryos that look normal when examined visually actually have chromosome abnormalities. The new method makes it possible to objectively select ovules that have the best chance of success without altering the integrity of the embryos.

A team led by Prof. Marc-André Sirard at the Universite Laval (Québec, Canada) developed a new method for detecting genetic markers. Eggs recovered in the course of the IVF process are surrounded by follicular cells that are removed before the actual fertilization procedure begins. Prof. Sirard explained, "While in the ovaries, these cells and the eggs are in very close interaction. A first experiment we conducted on bovine follicular cells led us to believe that these cells might possess specific markers that would be able to give us information about the quality of an egg.”

In a study involving 40 women recruited in a fertility clinic, the investigators compared follicular cells surrounding eggs that ultimately led to successful pregnancies--i.e., "good” eggs--to cells surrounding ovules that did not result in pregnancy. This comparison led to the identification of five genes expressed more abundantly in follicular cells surrounding good eggs.

The new genomic tool could also solve an ethical problem confronting both fertility clinic doctors and the people who consult them. In order to increase the chances of pregnancy, many embryos are implanted simultaneously into the woman in the hope that at least one will survive. This procedure along with improved IVF techniques has led to an increase in multiple pregnancies. "By selecting the embryo with the best potential, it would be possible to limit the number of embryos transferred, and thus the number of multiple pregnancies, while maintaining good success rates,” concluded Prof. Sirard.


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