Down syndrome is caused by a problem with a baby’s chromosomes. Normally, a person has 46 chromosomes. But most people with Down syndrome have 47 chromosomes. In rare cases, other chromosome problems cause Down syndrome. Having extra or abnormal chromosomes changes the way the brain and body develop.
You are older when you get pregnant. Many doctors believe that the risk increases for women age 35 and older.
You have a brother or sister who has Down syndrome.
You had another baby with Down syndrome.
If you’ve had a baby with Down syndrome and are planning another pregnancy, you may want to talk to your doctor about genetic counseling.