As women age, their ovarian reserve and oocyte integrity (function and normal chromosome number), gradually decrease.
In women, germ cell replication is completed at birth, oocytes remain arrested at stage I of cell division for up to 50 years and division resumes prior to ovulation. As women age, errors in DNA occur more frequently because divisions are of lower fidelity and this leads to abnormal chromosome number.
Taken together, these events explain the age-related decline in reproductive capacity (e.g. low rates of natural conception) and the poor results obtained with assisted reproduction technologies (ARTs). Women also experience an increased risk of pregnancy complications (perinatal morbidity and mortality) and of adverse perinatal and post-natal offspring outcomes as they age.
Finally, female fertility reaches a natural limit and altogether ceases with menopause.