It's a discovery that gives new hope to those dealing with infertility.

One out of every six couples struggles with conceiving, and even when they turn to in-vitro fertilization, many of the embryos generated aren't viable.

Researchers at the University of Montreal Hospital Centre say they've found one of the reasons many embryos generated during IVF have defects.

“Many of the embryos are losing their quality during the culture, and at the day of the transfer, we have fewer embryos than expected a few days before,” said Dr. Jacques Kadoch, medical director of the CHUM fertility clinic.

About half the embryos generated during in-vitro fertilization contain cells with an abnormal number of chromosomes.

“It's the process of cell division as the embryos are developing that goes wrong and leaves the cells within the embryos having the wrong number of chromosomes,” said Dr. Greg Fitzharris, a researcher at the CHUM research centre.

Called aneuploidy, that abnormality increases the risk of implantation failure and miscarriage.

“Probably about half of the embryos in fertility clinics have this particular type of problem,” said Fitzharris.

For the first time, Fitzharris and his research team have found one possible reason why these defects occur.

“The students in the lab seem to have found that a mechanism that normally prevents this type of error, called the spindle checkpoint, doesn't work very well in embryos,” he said.

Using embryos from lab mice, researchers found they could manipulate that checkpoint mechanism with a synthetic drug, reducing the chance of error by about half.

The discovery has a lot of potential, said Kadoch.

“If we can reduce this risk, we will increase the number of embryos available the day of the transfer, so the potential to get pregnant from an IVF cycle will be much higher,” he said.

Using this method clinically in humans is still a long way off, though. The team first has to conduct safety tests to see whether mice born from treated embryos are healthy.

“If we can reduce the stress for the couple, it would be great, and this technology could be a new hope for these couples,” said Kadoch.