New genomic technology is reshaping perinatal screening, which is testing before and during pregnancy to assess the health of a baby. Now pregnant women can have their baby initially screened for genetic disorders, such as Down syndrome, through the use of a newer blood test that evaluates DNA from the placenta present in the mother’s blood stream. Another test for couples planning a family uses a single blood sample to assess whether future children might be at risk for developing a genetic disease.
“It’s an exciting time in perinatal testing,” explains Myra Wick, M.D., Ph.D. “DNA sequencing and molecular technology has improved and become more cost effective. These tests are important for family planning prior to pregnancy as well as planning for the care of a child who is found to have a genetic disorder during pregnancy. ”
Three state-of-the-art perinatal genetic tests are highlighted below. Researchers from the Center for Individualized Medicine have helped implement several of these tests, which use a personalized medicine approach in perinatal screening.
Cell free DNA (cfDNA) testing
Mayo Medical Laboratories recently launched a blood test to screen for the most common chromosome disorders diagnosed in pregnancy, such as Down syndrome. It’s known as a cell-free DNA (cfDNA) test and screens the mother’s blood, which contains DNA from the placenta, for genetic changes linked to genetic disorders. The new test generally performs better than traditional tests, with a higher detection rate and lower false positive rate in most situations.
As Dr. Wick explains, this test provides a safe, cost effective option for pregnant women who may be at risk for having a child with a genetic disorder because of their family history or age.
“Prior to this new test, mothers had the option of traditional first and second trimester screening or invasive testing, which can increase the risk for miscarriage. We now also have the option to screen with the cfDNA test. If the blood test comes back showing a potential risk for genetic disorders, parents will be counseled regarding further testing to confirm the diagnosis. These tests include chorionic villus sampling, in which a small sample is taken from the placenta, or amniocentesis, in which a small sample of amniotic fluid is removed from the uterus,” explains Dr. Wick.
The out of pocket cost for the new blood test varies depending on insurance coverage, and the specific laboratory performing the testing; a general estimate is approximately $350. Results are usually returned within one week.
Expanded carrier screening
In the past, couples underwent genetic screening prior to having a child if they had a family history of a particular genetic disorder or if their ethnic background was associated with certain genetic diseases. In these cases, couples were tested for only a defined, small set of genetic disorders. Today many people are uncertain of their heritage or may be descendants of multiple ethnic backgrounds, making it hard to select a defined group of genes for testing.
“It’s an exciting time in perinatal testing. DNA sequencing and molecular technology has improved and become more cost effective. These tests are important for family planning prior to pregnancy as well as planning for the care of a child who is found to have a genetic disorder during pregnancy. ” - Dr. Myra Wick
Now couples can be tested for approximately 100 genetic disorders simultaneously with expanded carrier screening. For the test, each prospective parent provides a blood sample to screen for genetic changes linked to a genetic disorder.
“Expanded carrier screening looks at a broad range of genes linked to genetic diseases. Most of these disorders are inherited. With this testing, approximately 30 percent of the individuals tested have a genetic change linked to a genetic disorder. However, a couple is only at risk for having an affected child if both parents have a genetic change for the same disorder. This occurs in about five percent of the couples,” says Dr. Wick.
Depending upon insurance coverage, the test costs approximately $350. Test results are returned within one to two weeks.
Whole exome sequencing (WES)
In rare cases, an ultrasound during pregnancy reveals that the baby has several medical problems. Traditional genetic testing may not identify a diagnosis. Now whole exome sequencing (WES), which looks at most of the genes linked to growth and health, is being used to pinpoint the baby’s condition.
For this testing, an amniocentesis is performed first to obtain amniotic fluid for DNA analysis.
“At Mayo, we use whole genome sequencing to diagnose rare genetic diseases in children or adults, finding a diagnosis for 30 percent of the patients tested. Now we are beginning to use WES in the prenatal setting for the babies with complex medical problems. Results from this testing can be used to plan for a care for an infant who will be born with several medical concerns. In addition, parents can use this information for future family planning,” says Dr. Wick.
Whole exome sequencing can cost up to $8,000, depending upon the specific test and insurance coverage. Results from this more complex screening usually take several weeks, depending upon the specific test being used.
Seek genetic counseling before selecting a perinatal or prenatal genetic test
Dr. Wick’s suggests that you ask your health care provider about genetic testing and recommends that all prospective and expectant parents consult with a medical geneticist or genetic counselor prior to undergoing any genetic screening. These professionals can help couples understand all genetic test options available, what test results may reveal, and options for medical care for a child affected with a genetic condition.
If your provider is at a large medical center, genetic counseling should be available. At smaller facilities, your primary provider may order initial blood tests, but you may be referred to a larger facility if test results indicate you need genetic counseling.
Learn more about individualized medicine
Join us at Individualizing Medicine 2017: Advancing Care Through Genomics. The Mayo Clinic Center for Individualized Medicine, with support from the Jackson Family Foundation, is hosting the sixth annual genomics conference, October 9–10, in Rochester, Minnesota.
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