If you have any risk factors for having a fetus with a birth defect, talk with your doctor or a genetic counselor to help you decide which screening or diagnostic tests will be useful for you.

You may be at risk for having a fetus (baby) with birth defects because:

• Of your age. As you get older, you have a greater chance of having a baby with a birth defect. Many doctors use 35 and older as the age for higher risk.
• You or the baby's father carries an abnormal gene that is known to cause a disease, such as Tay-Sachs disease, sickle cell anemia, or cystic fibrosis.
• You or the baby's father has a family history of a genetic disorder or birth defect.
• You or the baby's father has a child who has a genetic disorder or birth defect.
• You have diabetes.
• You have used a medicine that is known to cause birth defects. Talk to your doctor about any medicine you have taken in the months before or during your pregnancy.

Women with known risk factors are usually offered a chorionic villus sampling in the late first trimester or an amniocentesis in the second trimester. If you have an amniocentesis, a triple or quadruple screen test for Down syndrome and birth defects is not necessary.