For the first time, scientists have identified a protein which they claim is responsible for increasing the risk of infertility, miscarriage and birth defects in older women.
It has been found that babies born to women in their late thirties and forties face an increased risk of disability due to eggs containing the wrong number of chromosomes, but the underlying cause was not known.
But, researchers at Newcastle University and Newcastle Fertility Centre identified the protein called cohesin, which helps cell division, declines dramatically as women aged.
Without enough of the protein, according to the scientists, eggs split in an uneven way, causing “messy” cell division that leads to an abnormal number of chromosomes, the Telegraph reported.
During reproduction, according to the scientists, the chromosomes in a cell form into pairs before dividing equally.
Cohesins hold chromosomes together by entrapping them in a ring, which is essential for them to split evenly during cell division.
For their study, researchers led by Dr Mary Herbert, used eggs from young and old mice to show that cohesin levels declined gradually as females got older.
This resulted in weakened cohesion between chromosomes and failure to divide equally during the halving of chromosome number in eggs of older females.
Eggs that were defective in this way may fail to develop, resulting in infertility, miscarriage or birth defects.
Dr Herbert, a reader in reproductive biology at the Institute of Ageing and Health, said further research would be carried out to see why cohesin was lost with age.
“If we can understand this, we will be in a better position to know if there is any possibility of developing interventions to help reduce cohesin loss,” she said.
“Undoubtedly, the best way for women to avoid this problem is to have their children earlier.”