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    Prenatal Testing & Genetic Counseling

    Prenatal testing can provide information about your baby's health before he or she is born. Consider the timing and what the tests can reveal.

    Who should have a screening test?

    You may benefit from genetic counseling and prenatal testing if:

    • You are pregnant and under age 35 but would like more accurate screening for Down syndrome
    • You are pregnant and will be 35 years or older on your due date
    • You are pregnant with an abnormal screening test result (for example, a positive expanded AFP blood test or integrated screening result)
    • You have had an ultrasound of your fetus showing a possible birth defect
    • You have already had a child or other close relative with a birth defect or genetic disease
    • You and your partner are carriers of a recessively inherited disease such as Tay-Sachs, sickle cell anemia, cystic fibrosis, or thalassemia
    • You are a carrier of an X-linked disease such as Fragile X, hemophilia, or muscular dystrophy
    • You and your partner are closely related (such as first cousins)
    • You have been exposed to medications, X-rays or other agents during your pregnancy that may be harmful to the developing fetus

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    What is genetic counseling?

    Specially trained genetic counselors provide information and support to individuals and families, addressing concerns about birth defects or inherited diseases before or during pregnancy. They also discuss family and personal health history to determine the chance that fetal disorders might occur and present appropriate options for prenatal testing.
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    What are screening tests and what types are available?

    Screening tests help identify women who are at increased risk of having babies with certain chromosomal abnormalities such as Down syndrome, selected inherited diseases such as cystic fibrosis, or physical birth defects such as spina bifida. The tests pose no risk to the pregnancy and identify many, but not all, women who are carrying fetuses affected with the conditions that are being screened.
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    First Trimester Screen

    Also known as the combined screen, the test offers the earliest screening for Down syndrome in a pregnancy. Between 11 and 14 weeks of pregnancy, a specialized ultrasound called the Nuchal Translucency (NT) is performed and a woman’s blood is drawn. The NT ultrasound is performed exclusively by doctors and sonographers who have special certification to perform this test. It involves measuring a small pocket of fluid at the back of the baby’s neck. Results from this test are available in about one week. This test screens for Down syndrome and trisomy 18 (a rare genetic disorder of chromosomes). This test does not screen for spina bifida.
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    Integrated Screen

    Integrated screen is a screening test that offers the highest detection rate for Down syndrome and is done in two stages. The first stage is performed between 11 and 14 weeks of pregnancy, which includes the specialized NT ultrasound and a blood draw for the mother. The second phase is an additional blood draw performed between 15 and 20 weeks of pregnancy. The results are available one week after the second blood draw. The integrated screening also offers the highest detection rate for trisomy 18 and screens for spina bifida.

    These screening tests are alternatives to the Expanded AFP (XAFP) blood test that is widely available from obstetricians. Information booklets about the XAFP test are available at your obstetrician’s office.
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    Ultrasound

    An ultrasound examination uses high frequency sound waves to create a visual image of fetal structures. The ultrasound allows evaluation of the anatomy of the
    baby, number of fetuses present, fetal growth, due date confirmation, determination of placental positions and other information about the pregnancy that can be useful to you and your doctor.
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    Targeted Ultrasound Examination

    In pregnancies at increased risk for specific genetic conditions or physical abnormalities, ultrasound may be used to examine a specific organ system or part of the body in an attempt to detect problems before birth.
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    Carrier Screening

    Individuals may have an increased chance of being a carrier of some genetic diseases based on their ethnic background and family history. For example, cystic fibrosis is more common in Caucasians. A genetic counselor will discuss what carrier screening options may be appropriate for you.
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    What Are Diagnostic Tests & What Types Are Available?

    Diagnostic tests identify chromosome abnormalities such as Down syndrome. We can test for other genetic diseases including cystic fibrosis and thalassemia, if the fetus is determined to be at risk. Because cells are tested directly from the fetus or placenta, the results are diagnostic (greater than 99 percent accurate for chromosome results). However, because it is necessary to enter the womb to obtain the cells, there is a small risk of miscarriage due to the procedure. At our center, the risk of miscarriage due to either amniocentesis or CVS is less than 1 in 200.
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    Chorionic Villus Sampling (CVS)

    CVS is a procedure in which a small amount of tissue (chorionic villi) is obtained from the placenta between 10 and 13 weeks of pregnancy. The tissue is then analyzed for chromosome studies and, if indicated, specific genetic diseases. CVS provides the earliest diagnostic test results for Down syndrome and other chromosome problems. (CVS cannot screen for spina bifida). Approximately one percent of CVS results will be unclear or indeterminate. Most fetuses screened are normal, but additional testing, such as amniocentesis, may be indicated.
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    Amniocentesis

    Amniocentesis is traditionally performed between 16 and 20 weeks of pregnancy. During the procedure, a thin needle is inserted through the mother’s abdomen into the amniotic fluid surrounding the fetus. A small amount of fluid is removed and analyzed for chromosome abnormalities, spina bifida and, if indicated, specified genetic diseases.
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