Health Library

Genetic screening is a process used to determine a child's risk of inheriting certain diseases or birth defects from his or her parents. Couples planning to have a baby might be concerned about illnesses that have occurred in family members. The best time to have a genetic screening done is before you get pregnant, but it can also be done during your first prenatal visit or later in your pregnancy.

There are several tests that look for different genetic disorders.

Keep in mind that genetic testing is not done for every pregnancy. Some have an increased risk of having a child with a genetic condition. Here are some common reasons your doctor may recommend genetic screening :

• Mother or father has family members with inherited disorders
• Mother is 35 years old or older when you deliver your baby.
• Previous child with a hereditary disease or birth defect.
• Previous stillbirths or several miscarriages.
• Abnormalities in the pregnancy such as too much or too little serum alpha fetoprotein (AFP).

Conditions that your doctor may screen for include:

• Tay-Sach's disease is a brain disorder, which is more common in people of Eastern European (Ashkenazi) Jewish descent, that causes early death.
• Thalassemia causes abnormal red blood cells. The condition is more common in people from southeast Asia, China, and Mediterranean countries, such as Greece and Italy.
• Hemophilia is a blood clotting disorder.
• Cystic fibrosis , caused by two defected genes, affects the lungs and pancreas.
• Sickle cell anemia , which is more common in African Americans of sub-Saharan origin, affects the red blood cells.

You should find out about the medical history of your family, including hereditary diseases in your mother's and father's families. If possible, ask your parents and your partner's parents about any abnormalities, disabilities, or intellectual disability in the family. Make a record of any of the following personal information:

• Miscarriages
• Exposure to environmental hazards before or during pregnancy (such as x-rays or other radiation; chemicals used at work, home, or with hobbies)
• Any prescription or nonprescription drugs you took before pregnancy or before you knew you were pregnant
• Any history of alcohol or drug use

During the genetic screening process, your doctor will ask you and your partner for a detailed family history of diseases, disorders, and birth defects. You may be given blood tests. If you are already pregnant, you might be given tests to examine the chromosomes and condition of the fetus. Examples of genetic screening tests given during pregnancy include:

• Blood tests to check the levels of alpha fetoprotein, with possible follow-up tests to look for neural tube defects
• Ultrasound scans to check for birth defects of the brain, heart, spine, arms, legs, and other organs
• Chorionic villus sampling (CVS) to check for chromosomal abnormalities
• Amniocentesis to check for chromosomal abnormalities

After the screening and tests, your doctor will discuss the results with you and make recommendations about any treatment that may be beneficial. Treatment is a personal choice that is left entirely up to you. Your doctor should provide you with lots of information about treatment options so that you can make informed choices.