Why older women fail to conceive
As women get older the chances of infertility, birth defects and developmental disabilities go up. These risks often relate to errors in chromosomes in the egg.
By examining the eggs from mice at different ages, scientists showed that weakened chromosome cohesion in older mice caused eggs to divide abnormally, leading to extra or missing chromosomes in the daughter cells.
Older mice had far less of a protein called cohesin that helps form a cell body called the centromere. This ensures chromosomes align and separate during cell division. In the mice, weakened centromere cohesion explained 90% of age-related chromosomal abnormalities.
As the cohesin proteins are laid down in the human egg before birth, it is possible that the birth defects and infertility associated with human maternal age are also due to falling levels of cohesin.