Age
Age plays a major part because it has been found that women older than the age of 35 have a higher risk of miscarriage than younger women. At age 35, there is about a 20 percent risk, at age 40, the risk is about 40 percent, and at the age of 45, the risk of miscarriage is about 80 percent. The older the woman is, the more vulnerable the pregnancy is, because eggs stored in the ovaries are vulnerable to damage over time.