Why Does Female Fertility Decrease Significantly After Age 35? New Research May Have Pinpointed the Reason

FitzHarris indicated these aneuploid eggs come with risks. With two few chromosomes, “… they’re nonviable, which means a woman can’t carry a pregnancy to term and she has a miscarriage,” he said. On the other hand, if there are too many chromosomes, this increases the chance of a birth defect, such as Down syndrome.

Previously, scientists understood aneuploid eggs were caused by a failure of the glue-like substance that helps keep chromosomes together.

This research theory, known as “cohesion-loss” hypothesis, identified the female glue holding the chromosomes together becomes less effective as women age, thereby disrupting a successful pregnancy. The CRCHUM study led by FitzHarris does not contradict those findings. However, it reveals a separate, additional problem that starts even earlier with older eggs not having the right number of chromosomes to begin with.

Researchers will now consider both theories as they look for innovative strategies to stop aging human eggs from carrying defects, and for the female glue to perform as it should.

FitzHarris points out that solving these aging-egg behaviors is a “complicated and multi-faceted” challenge.” However, he hopes further, targeted research will lead to new fertility treatments that will help older women to become pregnant and successfully carry a pregnancy to term.

“It’s still in its early stages but we’re currently using these findings to try and devise strategies that get old eggs to behave like young eggs,” FitzHarris said.