Public Release: 

Abnormalities in pregnancies with failures for noninvasive prenatal testing

Society for Maternal-Fetal Medicine

In a study to be presented on Feb. 6 in an oral concurrent session at 1:15 p.m. PST, at the Society for Maternal-Fetal Medicine's annual meeting, The Pregnancy Meeting™, in San Diego, researchers will report on the high rate of chromosomal abnormalities in patients in whom noninvasive prenatal testing fails to provide results.

Noninvasive prenatal testing has become popular with many physicians in screening pregnant patients. The study, titled Chromosomal Abnormalities Detected in Patients with Failure to Obtain Test Results Using Non-invasive Prenatal Testing, looked at noninvasive prenatal tests in a total of 4,446 pregnancies. The tests were performed from October 2012 to June 2104. High risk women were offered noninvasive prenatal tests per the American Congress of Obstetricians and Gynecologists guidelines and tests were done at an outside laboratory. Results were reported as "low risk", "high risk", or, if no result was obtained, as "redraw request." The incidence of chromosomal abnormalities in the RR group was compared to the entire cohort.

The study concluded that there is a high rate of chromosomal abnormalities in patients in whom NIPT fails to provide a result. Nearly half of tests will again fail on subsequent NIPT attempts.

"This is important information for patients and providers and requires clear understanding on how to interpret test results and appropriate follow up," explained John Turocy, M.D., one of the researchers of the study who is also presenting the findings at the SMFM annual meeting.

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Abstract 65: Chromosomal abnormalities detected in patients with failure to obtain test results using non-invasive prenatal testing.

Authors: John Turocy3, Carol Norem2, Bruce Blumberg1, Mary Norton4 1Kaiser Permanente Northern California, Genetics, and Graduate Medical Education, Oakland, CA, 2Kaiser Permanente Northern California, Genetics, Oakland, CA, 3Kaiser Permanente Northern California, Genetics, and Obstetrics and Gynecology, Modesto, CA, 4University of California, San Francisco, Department of Obstetrics, Gynecology and Reproductive Sciences, San Francisco, CA

Objective: To determine the incidence of chromosomal abnormalities in pregnancies with failed results using noninvasive prenatal testing (NIPT) in the Kaiser Permanente Northern California Regional Prenatal Screening Program.

Study Design: All results of NIPT performed from October 2012 to June 2014 were collected. High risk women were offered NIPT per ACOG guidelines; tests were done at an outside laboratory. Results were reported as "low risk", "high risk", or, if no result was obtained, as "redraw request" (RR). The incidence of chromosomal abnormalities in the RR group was compared to the entire cohort using chi square.

Results: NIPT was drawn in a total of 4446 pregnancies, with 102 (2.3%) pregnancies having an initial result of RR. Of the RR group, 63 chose redraw and 39 declined. Results of the 63 who chose redraw showed 32 (51%) with low risk; 5 (8%) with high risk; and 26 (41%) who failed to yield a result again. Thus, a total of 65 (1.5%) out of the 4446 had no final result on either one or two blood draws; 4219 had low risk results (94.9%) and 162 (3.6%) had high risk results. Of the 65 with no results, 43 (66.2%) had no chromosomal analysis, 13 (20%) had normal chromosomes, and 9 (13.8%) had abnormal chromosomes. Abnormalities detected were triploidy (3), T18 (3), T13 (1), T20 (1), and 45,X (1). In cases where results were not obtained due to insufficient fetal cfDNA, 7/52 (13%) had abnormal chromosomes, whereas cases due to high variance in cfDNA counts had 2/13 (15%) abnormal chromosomes. The rate of chromosomal abnormalities in patients with no final results (9/65; 13.8%) was significantly higher than in the overall cohort (108/4446; 2.4%), p=0.0001.

Conclusion: There is a high rate of chromosomal abnormalities in patients in whom NIPT fails to provide a result. Nearly half of tests will again fail on subsequent NIPT attempts. This is important information that patients and providers should consider in choosing the type of follow up for these cases.

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