You can do nothing to prevent Down's syndrome. If you already have a child with Down's syndrome, you are definitely at high risk of having another child with Down syndrome. You may want to consult your gynaecologist or genetic counselor before becoming pregnant again.
Your gynaecologist or a genetic counselor can help you understand your chances of having a child with Down syndrome. He or she can also explain the prenatal tests that are available and help explain the pros and cons of…