#36: Prenatal aneuploidy screening using cell-free DNA

Abstract

Recent advances in technology have created exciting opportunities to expand and improve genetic testing options that are available to women during pregnancy. However, the novelty and complexity of these technologies, combined with the commercial interest to implement these tests rapidly into routine clinical care, have created challenges for physicians and patients and potentially will lead to misunderstanding, misuse, and unintended consequences. The purpose of this document was to aid clinicians in their day-to-day practice of counseling patients regarding prenatal aneuploidy testing options with cell-free DNA screening, which includes how it compares to current testing methods, potential benefits and harms, and its limitations and caveats.

Use of Genetic Testing after Abnormal Screening Ultrasound: A Descriptive Cohort Study

“…Recent recommendations by ACOG and SMFM support the use of NIPS after abnormal ultrasound only when the patient declines invasive testing [3, 4]. Similarly, the International Society of Ultrasound in Obstetrics and Gynecology and American College of Medical Genetics both recommend diagnostic testing after abnormal ultrasound findings [13].…”

“…NIPS is a screening test, developed to test for common trisomies, performed by evaluation of fetal cell-free DNA collected from maternal plasma [3]. While NIPS is not the primary recommendation for testing after abnormal ultrasound, it may be an option for patients with ultrasound abnormalities who decline invasive testing [3, 4]. …”

Pre- and post-test genetic counseling for chromosomal and Mendelian disorders

“…Current clinical guidelines concerning cell free DNA screening for aneuploidy emphasize autonomous reproductive choices and the provision of balanced pretest counseling and information to patients. 23, 66, 20, 67 In order to meet this challenge, obstetrical providers must develop new methods of pre-test counseling that present the important elements of testing options in a framework patients can comprehend. Written and web-based educational materials that are understandable and unbiased for patients will also enhance the pre and post-test counseling process.…”

“…67 While cfDNA testing is often advertised as being highly accurate, patients should be aware that in the event of a positive result, the likelihood that the pregnancy is affected depends on factors including her age, results of other screening tests and her pregnancy and family history. In the low risk population, the chance that a positive result is a false positive result may be similar to or even exceed the likelihood of a true positive (see Table 1).…”

“…87 In addition, “no result” cfDNA results occur in up to 8% of cases, and because such results are associated with increased risk for fetal aneuploidy, genetic counseling, comprehensive ultrasound evaluation and invasive diagnostic testing should be offered. 2367, 87 …”