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Prenatal Tests

A screening test can help determine if a pregnancy is at a higher risk for a specific problem. Screening tests cannot tell you for certain if a baby has a problem, only whether it is more or less likely.

There is no risk of miscarriage from these tests. They may help you decide whether you want to pursue further diagnostic tests.

Our list of questions to consider and our guide to choosing a prenatal test may also help you decide which tests are right for you.

Genetic screenings

First trimester screening
Integrated screening
Sequential screening
Maternal serum screening
Ultrasound
Cystic fibrosis screening
Genetic carrier screenings

Diagnostic tests

Amniocentesis
Chorionic villus sampling

First trimester screening

This test combines ultrasound and maternal blood testing. Ultrasound is used to look at the fluid-filled space behind the baby's neck, known as nuchal translucency. The maternal blood test looks at the levels of three hormones. This test is done between 11 and 13 weeks of pregnancy, and estimates the risk of Down syndrome and trisomy 18.

Integrated screening

This test combines an ultrasound and two maternal blood tests. The first blood test is done with an ultrasound between 11 and 13 weeks of pregnancy. The second blood test is performed between 15 and 20 weeks. Results are available only after the second blood test. This screening can estimate the risk of Down syndrome, trisomy 18 and spina bifida.

Sequential screening

This is a two-part test, similar to integrated screening. The difference is that women at highest risk will get a result in the first trimester. Then, instead of a second blood draw, they can then consider diagnostic testing. All others will have the second blood test and receive results between 15 and 20 weeks.

Maternal serum screening

This test, also known as the alpha fetaprotein or quad marker test, is a blood test performed between 15 and 20 weeks of pregnancy. It screens for Down syndrome, trisomy 18, and open neural tube defects such as spina bifida.

Ultrasound

This test, done between 18 and 20 weeks of pregnancy, can be used to screen for certain chromosome disorders such as Down syndrome. It can also provide information about the size, growth, and presence of twins, in addition to identifying certain birth defects. It carries no known risk and is the most frequently used method of prenatal screening.

Cystic fibrosis screening

This screening tests your blood to see if you carry the gene that causes cystic fibrosis (CF). To have CF, a baby must have two copies of this gene. Both parents have to be carriers to be at risk for having a child with CF. The chances of having a child with CF, for a couple of European descent with no family history of the disease, is around one in 3300. Instead of this test, you could opt to wait for the newborn cystic fibrosis screening required by the state of New Hampshire.

Genetic carrier screenings

Specific tests are available for certain genetic conditions that occur more often in particular ethnic groups. A child with one of these conditions must have two copies of the gene, one from each parent. Ethnic groups at higher risk include:

  • Northern European Caucasians (cystic fibrosis)
  • Greek, Italian, Southeast Asians, Hispanics (Thalassemia)
  • African Americans, Hispanics (sickle cell anemia)
  • Ashkenazi Eastern European Jews (Tay-Sachs disease, Canavan disease, familial dysautonomia, cystic fibrosis)

Diagnostic tests

Diagnostic tests are available to all pregnant women. The results from screening tests may lead you to consider diagnostic tests to confirm whether the baby actually has the condition you are concerned about. Both of these tests have a small risk of miscarriage.

Amniocentesis

This test collects amniotic fluid by inserting a needle through the abdomen into the amniotic sac surrounding the baby. Amniocentesis is routinely performed between 15 and 20 weeks to diagnose many chromosome abnormalities and neural tube defects.

Chorionic villus sampling (CVS)

This test obtains a sample from the placenta by inserting a needle through the abdomen or a catheter through the cervix. CVS is done between 10 and 13 weeks of pregnancy and can test for chromosome conditions and certain genetic problems. The major advantage of CVS is that diagnosis is possible earlier than with amniocentesis.

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