All women, regardless of their age, are at risk for miscarriage in the first trimester. However, this risk increases the older you are. In your 20s, your miscarriage risk is only 10 percent. By age 35, your risk is nearly 20 percent, and by age 40, it increases to 35 percent. One of the primary reasons for age-related miscarriage is the age of your eggs.
The older an egg is, the more likely there is a defect in the cellular division process. This can cause the resulting fetus to have abnormal chromosomal numbers. Some of these fetuses will not develop normally, and you will miscarry.
Having a Baby At 35 Associated with More Birth Defects?
Because chromosomal abnormalities are more common with age, a woman over 35 is at higher risk for delivering a baby with a chromosomal birth defect, such as Down syndrome, trisomy 13 and trisomy 18.
At 20, your risk of delivering a baby with Down syndrome is 1 in over 1,600. By age 30, 1 in 1,000 women will have a baby with Down syndrome. When you reach 35, this risk dramatically increases to 1 in 400. For other chromosomal abnormalities, a 20-year-old’s risk is 1 in 500, and by age 35, the risk increases to 1 in 200.