Down Syndrome (formerly called mongolism), named after Dr. Langdon Down, who described these children in 1866, occurs in one out of seven hundred births. The chance of having a Down Syndrome baby increases with the age of the mother.
- Women under age 23—1 in 2,000 births
- Women at age 30—1 in 1,300 births
- Women at age 35—1 in 400 births
- Women at age 40—1 in 90 births
- Women at age 45—1 in 32 births
- Women at age 50—1 in 8 births
Depending on how they are presented, these figures can be scary. If a doctor says to a mother, “At age thirty-five you have five times the chance of having a Down Syndrome baby than you did at age twenty,” that would scare many senior mothers from conceiving. Here’s how I present the risk factors to my patients who ask. At age twenty you had a 99.95 percent chance of not delivering a baby with Down syndrome; at age thirty-five your chances of not delivering a baby with Down Syndrome are 99.75 percent. Doesn’t that figure sound more reassuring? This is why, in my opinion, the “thirty-five-year-old scare” is too young, forty-five perhaps? Even at age forty-five you have a 97 percent chance of delivering a baby without Down Syndrome. So, for mothers of later childbearing age, these figures are looking up.
Because of these risk factors, we believe that it is unwarranted to scare a thirty-five-year-old mother into prenatal diagnostic tests (either amniocentesis or chorionic villi sampling). Weigh these facts: At age thirty-five your statistical chance of delivering a Down Syndrome baby is 0.25 percent. However, the risk of damage to a normal preborn baby during these tests may be around 1 percent. At present, the AFP (alpha fetal protein) test is inaccurate for the prenatal diagnosis of Down Syndrome and is a source of much needless worry to pregnant parents. Whether or not you have a prenatal diagnostic testing is an individual judgment call between you and your doctor. But remember, your doctor is legally obligated to offer these tests to any mother thirty-five years of age or older.