Cutting edge, non-invasive genetic testing at the St. Louis Fetal Care Institute can help determine, with up to 99 percent accuracy, if an unborn baby has specific genetic disorders.
This new testing method, called noninvasive prenatal testing (NIPT), can detect chromosome abnormalities such as Down syndrome (trisomy 21), Edwards syndrome (trisomy 18) and Patau syndrome (trisomy 13). The test can also determine a baby’s sex chromosome makeup.
“Using routine blood work we can analyze the fetal DNA that is in the mother’s bloodstream,” says Fetal Care Institute Genetic Counselor Rachael Bradshaw, MS, CGC. If there is a different than expected amount of material from certain chromosomes when the lab analyzes the sample there is likely a presence of a chromosomal disorder in the baby.
“No prenatal test has 100 percent accuracy, but NIPT gives us a strong insight into a baby’s chromosome makeup,” says Bradshaw. NIPT is not a diagnostic test, so if the results are positive for any chromosome disorder, additional diagnostic testing CVS (chorionic villus sampling ) and amniocentisis is offered to confirm the results.
The test is offered to mothers who have risk factors such as a previous child with Down syndrome, trisomy 18 or trisomy 13 or those who are older than 35 years of age. It is typically conducted between 10 and 22 weeks gestation. The St. Louis Fetal Care Institute provides comprehensive genetic counseling services before and after all prenatal testing.
NIPT can help mothers avoid more invasive tests such as amniocentesis, which involves extracting a small amount of amniotic fluid from around the baby; or CVS, which collects an extremely small sample of the developing placenta. Unlike NIPT, both of these tests carry a small risk of miscarriage.
“However, it is important to realize that false positives and false negatives can occur with NIPT, and NIPT only tests for specific chromosome anomalies,” says Bradshaw. “Because of this, at this time, NIPT does not replace amniocentesis or CVS.”
Prenatal testing can help families, as well as the team at the Fetal Care Institute, prepare for the birth of the baby, including any special care that may be required after birth. It is important that all families carefully consider the benefits, risks and limitations of all genetic tests prior to pursuing them.
About The St. Louis Fetal Care Institute The St. Louis Fetal Care Institute is a partnership between SSM Cardinal Glennon Children’s Medical Center, SSM St. Mary’s Health Center, and Saint Louis University School of Medicine. Bringing together renowned maternal fetal medicine (MFM) specialists, pediatric and fetal surgeons, specialized nurses, cutting-edge technology, and a family-oriented approach, The Institute offers state-of-the-art diagnostic methods and treatment options for families whose unborn babies are facing medical challenges. It is one of the leading comprehensive fetal care programs in the country offering a variety of fetal interventions and treatments, including open and minimally invasive fetal surgery for babies in the womb.
Because NIPT is a new and powerful method of testing for fetal chromosome disorders, many professional organizations have issued statements reflecting their views about it:
ACOG (American College of Obstetrician and Gynecologists)
Noninvasive prenatal testing that uses cell free fetal DNA from the plasma of pregnant women offers tremendous potential as a screening tool for fetal aneuploidy. Cell free fetal DNA testing should be an informed patient choice after pretest counseling and should not be part of routine prenatal laboratory assessment. Cell free fetal DNA testing should not be offered to low-risk women or women with multiple gestations because it has not been sufficiently evaluated in these groups. A negative cell free fetal DNA test result does not ensure an unaffected pregnancy. A patient with a positive test result should be referred for genetic counseling and should be offered invasive prenatal diagnosis for confirmation of test results.
ISPD (International Society of Prenatal Diagnosis)
ISPD recognizes that NIPT can be helpful as a screening test for women who are at high risk for Trisomy 21 with suitable genetic counseling. A positive test should be confirmed through invasive testing.
NSGC (National Society of Genetic Counselors)
NSGC supports NIPT as an option for patients whose pregnancies are considered to be increased risk for certain chromosome abnormities. NSGC urges that NIPT only be offered in the context of informed consent, education, and counseling by a qualified provider, such as a certified genetic counselor. Patients whose NIPT results are abnormal, or who have other factors suggestive of a chromosome abnormality, should receive genetic counseling and be given the option of standard confirmatory diagnostic testing. http://www.nchpeg.org/index.php?option=com_content&view=article&id=387&Itemid=258