New York, March 16 - In a new study, scientists have identified genetic markers that allow the selection of eggs with the best chance of successful pregnancy after in vitro fertilisation -.


The study, by researchers at the Universite Laval in Canada, holds the potential of both improving the success rate of single embryo transfer as well as cutting the instances of multiple pregnancies, Sciencedaily reported.


Findings of the study, for which an international patent has been filed, have been published on the website of the journal Human Reproduction.


Eggs recovered in the course of the IVF process are surrounded by follicular cells, which are removed before the actual fertilisation procedure begins.


\'While in the ovaries, these cells and the eggs are in very close interaction,\' explained Marc-Andre Sirard, who led the study.


\'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.\'


With the help of 40 women recruited in a fertility clinic, researchers compared follicular cells surrounding eggs that ultimately led to successful pregnancies - in other words \'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.


Currently, the way to assess which embryos are to be transferred into a woman\'s uterus is based on visible criteria such as appearance and division rate.


\'At least 30 percent of embryos that look normal through visual examination nonetheless show chromosome abnormalities,\' explained Sirard, illustrating the limits of this type of assessment.


The method developed by Sirard\'s team makes it possible to objectively select ovules that have the best chance of success without altering the integrity of the embryos.


This 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.


Even if doctors now tend to transfer fewer embryos, multiple pregnancies still occur in 30 percent of couples who resort to IVF in North America and 23 percent in European couples.


\'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,\' said Sirard.