Genetic Testing During Pregnancy

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The amount of testing available before and during pregnancy can be confusing and overwhelming. Family history is still the best first step, but some testing may make sense even with no known health problems in the family. The information below provides an overview and introduction to prenatal genetic screening for general information  purposes. For more personalized advice, see how our Family Screens can help you create a Personalized Screening Plan.

Carrier testing

Carrier Testing for Childhood Conditions

Some inherited conditions result from genes that are hidden in the family.  Genes are made up of DNA and are passed from one generation to the next in a family. Genes determine how the body grows, develops, and functions. However, sometimes there is a mistake in a gene which causes the gene to not work properly. Some inherited conditions are called recessive conditions because as long as the person has at least one working copy of the gene, he or she will typically be healthy. A person with only one non-working copy of a particular gene is called a carrier. Parents who are carriers have a higher chance to have children with the inherited disease.

  •  Choices for testing

Some labs offer tests that screen for >250 diseases. It is also possible to order tests for just one condition if the parents know about a genetic disease in the family.

  •  Timing

Carrier testing is often first offered at the first prenatal appointment. However, carrier testing can be done at any time. In fact, having carrier testing before pregnancy allows more family options if people are found to have a higher chance to have a child with an inherited condition.

 

  •  Not all conditions

Carrier testing does not include all inherited conditions and can’t find all the carriers for the diseases on the tests. Therefore, knowing the health of your family can still be important. Mainstream Genomics' Family Screens are a starting point to decide whether any genetic screening or testing is right for you.

 

  •  Choices in pregnancy

There are a growing number of treatments for inherited diseases. However, many genetic diseases still cannot be cured or treated. Parents can choose, however, to test their pregnancies.

 

  •  Costs

Many health plans will cover carrier testing during pregnancy. Check your own policy for what your health plan offers. Several laboratories also offer carrier testing for a cash price of about $250 for the first partner and $100 for the second partner wifi the first is found to be a carrier.

non-invasive prenatal screening NIPS NIPT

Screening for Chromosomal Conditions

During pregnancy, some screening is available for certain chromosomal problems. Chromosomes contain the genetic material from the parents. Most people have 46 chromosomes, or 23 pairs.  In each pair, one copy is from the mom, and one is from the dad. Sometimes, a baby has an extra or missing copy of a chromosome. Certain prenatal screening tests predict the chances for some of these chromosome problems. Many, but not all, chromosomal conditions cause problems with development that can lead to things like severe learning problems or pregnancy loss.

  •  Types of Screening 

 

Non-invasive prenatal testing (NIPT)

Pregnant women’s blood has tiny amounts of genetic material from their babies. The placenta, or the membrane surrounding the baby during pregnancy, contains the same genetic material, or DNA, as the baby. Some fragments of DNA get loose in moms’ blood from the outer cells of the placenta. Those fragments of DNA can be studied in a laboratory in order to predict the likelihood that the fetus has the typical number of certain chromosomes. For example, NIPT is a screening test for an extra copy of chromosome 21, or Down syndrome, as well as other syndromes caused by extra or missing chromosomes. (You can read more in our blog post about Down syndrome.)​ 

There are different types of NIPT options, and they vary in the number and type of chromosomal conditions they detect. You can check the laboratory’s website to find out what specific conditions they include in their screening. In general, NIPT can find more chromosomal conditions than the other chromosomal screening tests listed next.

Nuchal translucency screening

The nuchal fold is the space behind the neck of the fetus. A specialist can measure that space using ultrasound in the late first trimester. Combined with a blood test on the mother for some hormones and other factors in her blood, a laboratory can predict the chances for certain chromosomal conditions, like Down syndrome.

 

Integrated screening

Using a blood sample from the mother during the first trimester and a second blood sample during the second trimester, a laboratory can predict the chances for certain chromosomal conditions, as with nuchal translucency screening.

 

Quad screening

A blood sample from the mother in the second trimester is used to predict the chances for certain chromosomal conditions. 

 

  • Timing

Screening for chromosomal conditions is done during pregnancy. Screening for extra or missing chromosomes cannot be done before pregnancy because the mistakes happen only in the egg or sperm.

  • Screening, not diagnosis

If a screening test finds a higher chance for genetic problems, it does not mean the child definitely has a problem. Prenatal diagnosis using amniocentesis or chronic villus sampling (CVS) would be needed to be certain.

 

  •  Limits of testing

None of these testing options screen for all genetic or inherited conditions. Even though chromosomes contain genetic material, screening tests aren't looking at individual genes, which are located on the chromosomes. They also do not look for all chromosomal problems,  because it looks for a subset of chromosome problems.

  •  Costs

Most insurance companies will cover NIPT screening, at least for higher risk women. Check your own policy for details.

Ultrasound Screening

Some physical birth defects cannot be diagnosed by looking at DNA but can be found by an ultrasound done by a specialist.  

  •  Examples

Couples with a family history of heart defects, for example, might need some special ultrasound exams.

  • Timing

Ultrasound can be done at any time during pregnancy for different reasons. When using ultrasound to look for physical birth defects because of a higher chance based on family medical history, the ultrasound is called a Level II ultrasound and is typically done between 18-20 weeks of pregnancy.

  •  Limits of ultrasound

Not all physical birth defects can be seen on an ultrasound.  Other factors, like the position of the baby at the time of the exam, could limit the view of the baby.

 

  •  Costs

Most insurance companies will cover ultrasound exams during pregnancy. 

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Prenatal Diagnosis

Special procedures called amniocentesis or chorionic villus sampling (CVS) can diagnose genetic problems in a fetus during the first or second trimester of pregnancy. 

  •  Types of conditions

Standard testing looks for chromosomal problems. Testing for single-gene conditions, if known to be in the family, can also sometimes be ordered.

 

  •  Limits of testing

Not all inherited conditions or birth defects can be found during pregnancy. Not all genes are studied.

  •  Options in pregnancy

Prenatal diagnosis may change where a woman delivers and allow the expecting parents time to learn about the condition and prepare. Other couples may choose special needs adoption or choose to end pregnancies based on this information. Rarely, treatments are available while in the womb.

 

  •  Risks

Amniocentesis or CVS require a sample from the fetus for testing. Getting the sample creates a small chance for a miscarriage.

 

  •  Costs

Most insurance plans cover prenatal diagnosis if there is a reason to offer it. Check your own policy for details.