The link between family health history and Down syndrome

March 1, 2021

If someone in your family has a child with Down syndrome, you may wonder if you will, too. Even though Down syndrome is a genetic condition, in most cases, it is not passed down from other family members.

Down syndrome (also called trisomy 21) is the most common chromosomal condition in the United States. About 1 in 700 babies (less than 1 percent) is born with Down syndrome. Many children with Down syndrome lead healthy, active lives.

Your family health history is a record of any health conditions and treatments that you, your partner and everyone in both of your families have had. Your family health history can help you and your health care provider identify genetic conditions that you may have inherited. Inherited means something that is passed from parent to child through genes. Genes are a part of your body’s cells that store instructions for the way your body grows and works.

What causes Down syndrome?

Chromosomes are the structures that hold genes. Each person has 23 pairs of chromosomes, or 46 in all. For each pair, you get one chromosome from your mother and one from your father. Babies with Down syndrome have an extra copy of chromosome 21. This extra copy changes the way the brain and body develop.

There are three types of Down syndrome: Trisomy 21 (the most common kind), translocation Down syndrome and mosaic Down syndrome. We don’t know for sure why Down syndrome happens, but these things can affect your risk of having a baby with the condition:

  • Your age when you get pregnant. Your risk of having a baby with Down syndrome increases as you get older, especially if you are age 35 or older. However, most children with Down syndrome are born to women under age 35 because younger women have far more babies.
  • Being a carrier of a certain type of Down syndrome. If you or your partner are a carrier of translocation Down syndrome, you carry a gene change for the condition, but you don’t actually have Down syndrome. Both men and women can pass translocation Down syndrome on to their children, but it’s rare.
  • Already having a baby with Down syndrome. If you already have a baby with Down syndrome, your risk for having another is higher.

Can you find out during pregnancy if your baby has Down syndrome?

Yes. Health care providers offer to test for Down syndrome as part of regular prenatal care (medical care you get during pregnancy). You can decide if you want to have these tests.

Use our family health history form to help you find out if certain health conditions run in your family. If you or your partner has a family history of Down syndrome, tell your health care provider or a genetic counselor. A genetic counselor is a person who is trained to help you understand genes, birth defects and other medical conditions that run in families and how they can affect your health and your baby’s health.