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Pregnancy Screening in Late Gestation

by
Patty Taneja, MS, LCGC
| May 12, 2016


The introduction of cell-free DNA (cfDNA)-based noninvasive prenatal testing (NIPT) has set the stage for a rapid shift in the paradigm of aneuploidy screening during pregnancy. NIPT is the first prenatal screening option outside of ultrasound evaluation available after 23 weeks gestation. Clinical validation studies of NIPT have mostly been limited to patients at a gestational age of less than 23 weeks who were also undergoing invasive prenatal procedures.1 Published studies evaluating fetal DNA fraction have found increased levels in the third trimester, and thus no technical barrier to offering NIPT later in pregnancy.2-5 The American College of Obstetrics and Gynecology (ACOG) issued Practice Bulletin #163 (PB163) on screening options for fetal aneuploidy in the general obstetric population, which now includes NIPT as an option for all women.6 Of the screening options detailed by ACOG, NIPT is the only test available after 22 weeks of gestation.6

Some providers may think that because pregnancy management options are limited at later stages of pregnancy, there is no need for screening options at this stage.7 However, the availability of prenatal screening results can aid clinicians in managing pregnancy and delivery options, and help expectant parents prepare for possible medical and/or psychosocial needs for their unborn child.8-9 A recently published study evaluates the clinical performance and clinical utility of NIPT at a gestational age of > 23 weeks of age. 

A total of 5,579 samples submitted for the verifi® noninvasive prenatal test through Illumina’s CAP-accredited CLIA certified clinical lab in Redwood City, CA with a gestational age of 23 weeks or greater were included in this study. The screen positive rate, turnaround time, and technical cancellation rate were similar to an all-gestation cohort.10 Clinical pre-test indication of ultrasound findings were significantly more common in the late gestation study cohort (p<0.0001). Additionally, ultrasound findings conferred higher positive predictive value (PPV) for testing. Lastly, this study provides case studies that show how the NIPT results were utilized by patients and providers to help with pregnancy management and delivery planning. 

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References:

  1. Bianchi DW, Platt LD, Goldberg JD, et al. Genome-wide fetal aneuploidy detection by maternal plasma DNA sequencing. Obstet Gynecol 2012;119(5):890-901.
  2. Wang E, Batey A, Struble C, Musci T, Song K, Oliphant A. Gestational age and maternal weight effects on fetal cell-free DNA in maternal plasma. Prenat Diagn 2013;33(7):662-6.
  3. Fan HC, Blumenfeld YJ, Chitkara U, Hudgins L, Quake SR. Noninvasive diagnosis   of fetal aneuploidy by shotgun sequencing DNA from maternal blood. Proc Natl Acad Sci U S A 2008;105(42):16266-71.
  4.  Birch L, English CA, O'Donoghue K, Barigye O, Fisk NM, Keer JT. Accurate and robust quantification of circulating fetal and total DNA in maternal plasma from 5 to 41 weeks of gestation. Clin Chem 2005;51(2):312-20.
  5. Galbiati S, Smid M, Gambini D, Ferrari A, Restagno G, Viora E, Campogrande M, Bastonero S, Pagliano M, Calza S and others. Fetal DNA detection in maternal plasma throughout gestation. Hum Genet 2005;117(2-3):243-8.
  6. ACOG. Screening for fetal aneuploidy. Practice Bulletin No. 163. American College of Obstetricians and Gynecologists. Obstet Gynecol 2016; epub ahead of print.
  7. SMFM. 2014 Apr 7. SMFM Statement: Maternal serum cell-free DNA screening in low risk women. Accessed 2016 Apr 15.
  8. Gregg AR, Gross SJ, Best RG, Monaghan KG, Bajaj K, Skotko BG, Thompson BH, Watson MS. ACMG statement on noninvasive prenatal screening for fetal aneuploidy. Genet Med 2013;15(5):395-8.
  9. DiNonno WO, Abuhamad AZ, Snyder HL. Value of non-invasive prenatal testing in the third trimester: a case report. National Society of Genetic Counselors Annual Education Conference. Boston, MA 2012.
  10. Taneja PA, Snyder HL, de Feo E, Kruglyak KM, Halks-Miller M, Curnow KJ, and Bhatt S. Noninvasive prenatal testing in the general obstetric population: clinical performance and counseling considerations in over 85 000 cases. Prenat Diagn. 2016 Mar;36(3):237-43.

The verifi® test was developed by, and its performance characteristics were determined by Verinata Health, Inc. (VHI), a wholly owned subsidiary of Illumina, Inc. The VHI laboratory is CAP-accredited and certified under the Clinical Laboratory Improvement Amendments (CLIA) as qualified to perform high complexity clinical laboratory testing. It has not been cleared or approved by the U.S. Food and Drug Administration.

 

 


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