Prenatal Genetic Counseling

Pregnant women may be amazed at the number and variety of prenatal tests available. Blood tests, urine tests, monthly medical exams, screening tests, and family history tracking all help to assess the health of a mom and her baby.

Genetic tests identify the likelihood of parents passing a genetic disease or disorder to their children. If your history suggests that genetic testing would be helpful, you may be referred to a genetic counselor. Or, you might choose to get genetic counseling yourself.

What Is Genetic Counseling?

Genetic counseling is the process of:

• checking family and medical records
• ordering genetic tests
• evaluating the results of these tests and records
• helping parents understand and reach decisions about what to do next

Genetic tests are done by analyzing small samples of blood or body tissues. They determine whether you, your partner, or your baby carry genes for some inherited disorders.

What Are Genes?

Genes are made up of DNA molecules, which are the building blocks of heredity. They're grouped together in specific patterns within a person's chromosomes, forming the unique "blueprint" for every physical and biological characteristic of that person.

Humans have 46 chromosomes, arranged in pairs in every living cell of our bodies. When the egg and sperm join at conception, half of each chromosomal pair is inherited from each parent. This newly formed combination of chromosomes then copies itself again and again during fetal growth and development, passing identical genetic information to each new cell in the growing fetus.

Current science suggests that every human has about 25,000 genes per cell. An error in just one gene (and in some instances, even a change in a single piece of DNA) can sometimes be the cause for a serious medical condition.

What Do Genetic Counselors Do?

Genetic tests yield complex results. Understanding what they mean is where a genetic counselor comes in.

Genetic counselors are professionals who have completed a master's program in medical genetics and counseling skills. They then pass a certification exam administered by the American Board of Genetic Counseling.

Genetic counselors can help:

• identify and interpret the risks of an inherited disorder
• explain inheritance patterns
• suggest testing
• lay out possible scenarios

They will explain the meaning of the medical science involved and provide support. If you haven't had genetic tests done yet, they may refer you to a doctor or a lab.

Who Should See a Genetic Counselor?

Most couples planning a pregnancy or who are expecting don't need genetic counseling. About 3% of babies are born with birth defects each year, says the Centers for Disease Control and Prevention (CDC). Many problems that happen are treatable. Cleft palate and clubfoot, two of the more common birth defects, can be surgically repaired, as can many heart defects.

The best time for genetic counseling is before a woman becomes pregnant. The counselor can help her understand any risk factors. But even during pregnancy, a meeting with a genetic counselor can be helpful.

Experts recommend that all pregnant women, regardless of age or circumstance, be offered genetic counseling and testing to screen for Down syndrome.

It's especially important to consider genetic counseling if:

• a standard prenatal screening test has an abnormal result
• an amniocentesis yields an unexpected result
• either parent or a close relative has an inherited disease or birth defect
• either parent already has children with birth defects, intellectual disabilities, or genetic disorders
• the mother-to-be has had two or more miscarriages or babies that died in infancy
• the mother-to-be will be 35 or older when the baby is born. Chances of having a child with Down syndrome increase with the mother's age.
• there's concern about genetic defects that happen often in an ethnic or racial group
• either parent is concerned about the effects of exposure to radiation, medicines, illegal drugs, infections, or chemicals

Meeting With a Genetic Counselor

Before you meet with a genetic counselor in person, you may be asked to gather information about your family history. The counselor will want to know of any relatives with genetic disorders, multiple miscarriages, and early or unexplained deaths. The counselor will also want to look over your medical records, including any ultrasounds, prenatal test results, past pregnancies, and medicines you took before or during pregnancy.

When you meet with the counselor, you'll go over any gaps or potential problem areas in your family or medical history. The counselor can help you understand the inheritance patterns of disorders and help assess your chances of having a child with those disorders.

The counselor will talk about risks that every pregnancy faces and risks that you personally face. Even if you discover you have a particular problem gene, science can't always predict the severity of the related disease. For instance, a child with cystic fibrosis can have debilitating lung problems or, less commonly, milder respiratory symptoms.

If more tests are needed, the counselor will help you set up those appointments and track the paperwork. When the results come in, the counselor will call you with the news and may ask you to come in for another discussion.

What Happens After Counseling?

Genetic counselors can help you understand your options and adjust to any uncertainties you face. But you and your family will decide what to do next.

If you've learned before conception that you and/or your partner are at high risk for having a child with a severe or fatal defect, your options might include:

• pre-implantation diagnosis. This is when eggs that have been fertilized in vitro (in a laboratory, outside of the womb) are tested for defects at the 8-cell (blastocyst) stage. Only nonaffected blastocysts are implanted in the uterus to establish a pregnancy.
• using donor sperm or donor eggs
• adoption
• taking the risk and having a child
• becoming pregnant and having specific prenatal testing

If you've had a diagnosis of a severe or fatal defect after conception, your options might include:

• preparing yourself for the challenges you'll face when you have your baby
• fetal surgery to repair the defect before birth. Surgery can only be used to treat some defects, such as spina bifida or congenital diaphragmatic hernia, a hole in the diaphragm that can cause underdeveloped lungs. Most defects cannot be surgically repaired.
• ending the pregnancy

Genetic counselors can share the experiences they've had with other families in your situation. But they will not suggest a particular course of action. A genetic counselor understands that what is right for one family may not be right for another.

Genetic counselors can, however, refer you to specialists for further help. Genetic counselors can also refer you to social workers, support groups, or mental health professionals to help you adjust to and prepare for your complex new reality.

What Else Should I Know?

Working with a genetic counselor can be reassuring and informative, especially if you or your partner have known risk factors. Talk to your doctor if you feel you would benefit from genetic counseling.

Many doctors have a list of local genetic counselors they work with. You also can contact the National Society of Genetic Counselors for more information.