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Genetic screening and diagnosis: Key advancements and the role of genetic counseling


 

Advances in imaging, panel testing

The most significant addition to the first-trimester ultrasound evaluation in recent years has been the systematic assessment of the fetal circulation and the structure of the fetal heart, with early detection of the most common forms of birth defects.

Structural assessment of the central nervous system, abdomen, and skeleton is also now possible during the first-trimester ultrasound and offers the opportunity for early genetic assessment when anomalies are detected.

Ultrasound imaging in the second and third trimesters can help refine the diagnosis of birth defects, track the evolution of suspicious findings from the first trimester, or uncover anomalies that did not present earlier. Findings may be suggestive of underlying genetic conditions and drive the use of “panel” tests, or targeted sequencing panels, to help make a diagnosis.

Features of skeletal dysplasia, for instance, would lead the genetic counselor to recommend a panel of tests that target skeletal dysplasia-associated genes, looking for genetic mutations. Similarly, holoprosencephaly detected on ultrasound could prompt use of a customized gene panel to look for mutations in a series of different genes known to cause the anomaly.

Second trimester details that may guide genetic investigation are not limited to ultrasound. In certain instances, MRI has the unique capability to diagnose particular structural defects, especially brain anomalies with developmental specificity.

Commentary by Christopher R. Harman, MD

Genetic counseling is now a mandatory part of all pregnancy evaluation programs. Counselors not only explain and interpret tests and results to families but also, increasingly, guide the efforts of the obstetrics team, including the maternal-fetal medicine specialist.

Dr. Christopher R. Harman, Chair and Sylvan Frieman, MD Endowed Professor in Obstetrics, Gynecology and Reproductive Sciences at the University of Maryland

Dr. Christopher R. Harman

The genetic counselor helps design screening for the whole patient population and focuses diagnostic testing in specific cases of screening concerns, family history, chromosomal abnormalities in prior pregnancies, and fetal abnormalities detected through ultrasonography or other prenatal surveillance. They also serve as a crucial link between the physician and the family.

The counselor also has a key role in the case of a stillbirth or other adverse pregnancy outcome in investigating possible genetic elements and working with the family on evaluation of recurrence risk and prevention of a similar outcome in future pregnancies. The details of poor outcomes hold the potential for making the next pregnancy successful.

Commentary by Amanda S. Higgs, MGC

Even in 2021, there is no “perfect baby test.” Patients can have expanded carrier screening, cell-free DNA testing, invasive testing with microarray, and all of the available imaging, with normal results, and still have a baby with a genetic disorder. Understanding the concept of residual risk is important. So is appreciation for the possibility that incidental findings – information not sought – can occur even with specific genetic testing.

Amanda S. Higgs, senior genetic counselor in the Department of Obstetrics, Gynecology and Reproductive Sciences, Univ. of Maryland

Amanda S. Higgs

Genetic counselors are there to help patients understand and assimilate information, usher them through the screening and testing process, and facilitate informed decision-making. We are nondirective in our counseling. We try to assess their values, their support systems, and their experience with disability and help them to make the best decisions for themselves regarding testing and further evaluation, as well as other reproductive decisions.

obnews@mdedge.com

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