Limitations of noninvasive screening
In our fetal heart program we see increasing numbers of referred patients who have chosen noninvasive cell-free fetal DNA screening (cfDNA) after a cardiac anomaly is detected on ultrasound examination, and who believe that their “low risk” results demonstrate very little or no risk of CHD. Many of these patients express a belief that noninvasive testing is highly sensitive and accurate for fetal anomalies, including CHDs, and are not easily convinced of the value of other genetic tests.
We recently conducted a retrospective chart analysis (unpublished) in which we found that 41% of cases of CHD with abnormal genetics results were not detectable by cfDNA screening.
In the case of atrial-ventricular septal defects and conotruncal abnormalities that often are more associated with common aneuploidies (trisomy 21, 18, 13, and 45 XO), a “high-risk” result from cfDNA screening may offer the family and cardiology/neonatal team some guidance, but a “low-risk” result does not eliminate the risk of a microarray abnormality and thus may provide false reassurance.
Other research has shown that noninvasive screening will miss up to 7.3% of karyotype abnormalities in pregnancies at high risk for common aneuploidies.6
While invasive testing poses a very small risk of miscarriage, it is hard without such testing to elucidate the potential genetic etiologies of CHDs and truly understand the problems. We must take time to thoughtfully counsel patients who decline invasive testing about the limitations of cfDNA screening for CHDs and other anomalies.
Dr. Turan is an associate professor of obstetrics, gynecology, and reproductive sciences, and director of the fetal heart program at the University of Maryland School of Medicine and director of the Fetal Heart Program at the University of Maryland Medical Center. Dr. Turan reported that she has no disclosures relevant to this Master Class. Email her at obnews@mdedge.com.
References
1. J Am Coll Cardiol. 1988 Oct;12(4):1079-86.
2. Pediatr Cardiol. 2019 Mar;40(3):489-96.
3. Ann Pediatr Cardiol. 2017 May-Aug;10(2):126-30.
4. Eur J Obstet Gynecol Reprod Biol 2018;221:172-76.