Counsyl Prelude™ Prenatal Screen

Delivering reliable results,
the first time

The Counsyl Prelude Prenatal Screen (NIPS) has an industry-leading low test failure rate of 0.1%, which means fewer unnecessary invasive procedures and less patient anxiety.

Why non-invasive prenatal screening

Every woman who wants to know more about her pregnancy should be offered non-invasive prenatal screening (NIPS).

100X lower
false positives

The false positive rate of NIPS is 100x lower than serum screening in patients in the general obstetric population.1

20X better
positive predictive value

Positive predictive value (PPV) is 20-fold higher than in standard serum screening.1

Recognized by
medical societies

Professional societies such as ACOG and ACMG endorse and/or recognize NIPS as a screening option for all pregnant women.2,3

Why Counsyl Prelude

Delivering reliable results, the first time

Excellent test performance which helps simplify practice workflow.

Personalized expert analysis of your patients’ samples through:

  • Custom algorithms and bioinformatics combined with expert manual review
  • Maximized test performance for each sample based on its own individual metrics

One test for all your patients

  • Including pregnancies with an ovum donor, patients with a high body-mass Index (BMI) and twin pregnancies

The Counsyl Prelude Prenatal Screen is designed to provide individualized analysis for each patient, while supporting your practice throughout the process so you can seamlessly incorporate prenatal genetic screening into your practice.

Focused conditions:

A primary focus on common aneuploidies, as recommended by societal guidelines,1 with options for additional testing

View full list >

Clear risk assessment:

Clarity of your patient’s true risk with individualized positive predictive values (PPV) and residual risk estimates to help inform next steps

Learn more about individualized PPV and residual risk >


The supporting services through Counsyl Complete helps seamlessly integrate non-invasive prenatal screening (NIPS) into your practice workflow.


We make it easy to inform and educate your patients about how non-invasive prenatal screening works.


We strive to make screening accessible for more patients.


We automate the management of results and follow up with patients.


Our board-certified genetic counselors are available on-demand for all Counsyl patients, not just those who screen positive.

Test Details

About the Prelude Prenatal Screen

The Counsyl Prelude Prenatal Screen is a non-invasive prenatal screen that uses cell-free DNA (cfDNA) to determine if a pregnancy is at an increased risk for common chromosome abnormalities, such as Down syndrome.

cfDNA screening has been shown to be superior to methods that use maternal age, ultrasound, and serum screening. This results in a lower false-positive rate and false-negative rate.2

The Prelude Prenatal Screen can be ordered with the ForesightTM Carrier Screen and offered to all women, including those with high BMI, an ovum donor or a twin pregnancy.


Sex Chromosomes


  • Microdeletion and sex chromosome screening are optional.

    While looking at sex chromosomes, we can report the predicted fetal sex.

Conditions covered

Common aneuploidies: Trisomy 21, Trisomy 18, Trisomy 13.
Optional analysis of sex chromosomes and microdeletions.

Who to screen

All pregnant women

When to screen

As early as 10 weeks into pregnancy

Sample type

One tube of blood

Turnaround time:

Approximately 1 week


Whole-genome sequencing

Get started today

Taking it has helped me sleep better because getting answers – one way or the other – is a huge relief.

Lacey, 37 (pictured with fiancé Sejin)

Counsyl Prelude Prenatal Screen patient, expecting her first baby girl


  1. Norton, M. et al Cell free DNA analysis for noninvasive examination of trisomy. The New England Journal of Medicine April 2015; 372: 1589-1597.
  2. Practice Bulletin No. 163: screening for fetal aneuploidy. Obstet Gynecol. 2016;127(5):e123–37.
  3. Noninvasive Prenatal Screening for Fetal Aneuploidy, 2016 Update: A Position Statement of the American College of Medical Genetics and Genomics. Obstetrical and Gynecological Survey. 2017 Jan 1;72(1):6-8.
  4. Taneja et al. Noninvasive prenatal testing in the general obstetric population: clinical performance and counseling considerations in over 85000 cases†. Prenatal Diagnosis 2016, 36, 1–7.
  5. Data on file
  6. Bianchi DW, Parker RL, Wentworth J, et al. DNA sequencing versus standard prenatal aneuploidy screening. N Engl J Med. 2014:370(9):799-808.
  7. Artieri, C. G., Haverty, C., Evans, E. A., Goldberg, J. D., Haque, I. S., Yaron, Y., and Muzzey, D. (2017) Noninvasive Prenatal Screening at Low Fetal Fraction: Comparing Whole-Genome Sequencing and Single-Nucleotide Polymorphism Methods. Prenat Diagn, doi: 10.1002/pd.503
  8. Bianchi DW, Platt LD, Goldberg JD, Abuhamad AZ, Sehnert AJ, Rava RP. Genome-wide fetal aneuploidy detection by maternal plasma DNA sequencing. Obstet Gynecol 2012, 119(5):890-901.
  9. Gil MM, Accurti V, Santacruz B, Plana MN, Nicolaides KH. Analysis of cell-free DNA in maternal blood in screening for aneuploidies: updated meta-analysis. Ultrasound Obstet Gynecol 2017;50:302-14.
  10. Gravholt CH, Juul S, Naeraa RW, Hansen J. Prenatal and postnatal prevalence of Turner's syndrome : a registry study. BMJ. 1996;312:16-21.
  11. Illumina, Inc. Analytical Validation of the verifi® prenatal test: Enhanced Test Performance for Detecting Trisomies 21, 18, and 13 and the Option for Classification of Sex Chromosome Status. 2012.
  12. Liao H, Liu S, Wang H. Performance of non-invasive prenatal screening for fetal aneuploidy in twin pregnancies: a meta-analysis. Prenat Diagn. 2017;37: 874-882.
  13. Rodis JF, Egan JF, Craffey A, Ciarleglio L, Greenstein RM, Scorza WE. Calculated risk of chromosomal abnormalities in twin gestations. Obstet Gynecol. 1990;76: 1037-1041.
  14. Simpson LL. Twin-twin transfusion syndrome. Am J Obstet Gynecol. Elsevier; 2013;208: 3-18.
  15. Snijders RJM, Sundberg K, Holzgreve W, Henry G, Nicolaides KH. Maternal age and gestation-specific risk for trisomy 21. Ultrasound Obstet Gynecol 1999;13:167-70.
  16. Snijders RJM, Sebire NJ, Cuckle H, Nicolaides KH. Maternal age and gestation age-specific risks for chromosomal defects. Fetal Diag Ther 1995;10:356-67.