Noninvasive prenatal testing for fetal trisomies in a
routinely screened first-trimester population
Kypros H. Nicolaides, MD; Argyro Syngelaki, RM; Ghalia Ashoor, MD; Cahit Birdir, MD; Gisele Touzet, MD
OBJECTIVE: We sought to assess performance of noninvasive prenatal
testing for fetal trisomy in a routinely screened first-trimester pregnancy
population.
STUDY DESIGN: This was a cohort study of 2049 pregnant women un-
dergoing routine screening for aneuploidies at 11-13 weeks’ gestation.
Plasma cell-free DNA analysis using chromosome-selective sequenc-
ing was used. Laboratory testing on a single plasma sample of 2 mL
was carried out blindly and results were provided as risk score (%) for
trisomies 21 and 18.
RESULTS: Trisomy risk scores were given for 95.1% (1949 of 2049) of
cases including all 8 with trisomy 21 and 2 of the 3 with trisomy 18. The
trisomy risk score was 99% in the 8 cases of trisomy 21 and 2 of
trisomy 18 and 1% in 99.9% (1937 of 1939) of euploid cases.
CONCLUSION: Noninvasive prenatal testing using chromosome-selec-
tive sequencing in a routinely screened population identified trisomies
21 and 18 with a false-positive rate of 0.1%.
Key words: first trimester, noninvasive prenatal diagnostics, prenatal
screening, trisomy 18, trisomy 21
Cite this article as: Nicolaides KH, Syngelaki A, Ashoor G, et al. Noninvasive prenatal testing for fetal trisomies in a routinely screened first-trimester population.
Am J Obstet Gynecol 2012;207:374.e1-6.
I
n the last 40 years, screening and
diagnosis of fetal aneuploidies has
shifted from second-trimester amnio-
centesis for advanced maternal age, with
a detection rate (DR) of trisomy 21 of
30% at false-positive rate (FPR) of 5%, to
first-trimester chorionic villous sam-
pling (CVS) in the high-risk group iden-
tified by screening with fetal nuchal
translucency (NT) and serum biochem-
istry, with DR of about 90% at FPR of
3-5%.
1,2
Invasive testing with CVS or
amniocentesis is diagnostic, but associ-
ated with the risk of miscarriage.
Recently, noninvasive prenatal testing
(NIPT) by analysis of cell-free DNA
(cfDNA) in maternal blood has shown
promise for highly accurate detection of
common fetal autosomal trisomies.
3
Analysis of cfDNA has been validated in
several clinical studies utilizing next-
generation DNA sequencing techno-
logy.
4-13
Clinical studies have primar-
ily included women identified by prior
screening, with maternal age and bio-
chemical and/or sonographic testing in the
first or second trimester of pregnancy, to
be at high risk for aneuploidies. It has
therefore been uncertain if the results of
NIPT in such high-risk pregnancies are
applicable to the general pregnancy
population.
The objective of this study is to assess
the performance of screening by NIPT
for trisomies 21 and 18 using a chromo-
some-selective sequencing method of
cfDNA in maternal plasma obtained
from a population undergoing routine
screening at 11-13 weeks’ gestation.
MATERIALS AND METHODS
Study population
The data for this study were derived from
analysis of stored maternal plasma ob-
tained during prospective first-trimester
combined screening for aneuploidies in
women with singleton pregnancies at-
tending for their routine first hospital
visit in pregnancy. In this visit, which
was held at 11
+0
-13
+6
weeks of gesta-
tion, we recorded maternal characteris-
tics and medical history and performed
an ultrasound scan to: firstly, determine
gestational age from the measurement of
the fetal crown-rump length; secondly,
diagnose any major fetal abnormalities;
thirdly, measure fetal NT thickness; and
fourthly, assess the nasal bone (NB) as
present or absent, the flow across the tr-
icuspid valve as normal or regurgitant
(tricuspid regurgitation [TR]), and the
a-wave in the ductus venosus (DV) as
normal or reversed.
1,2
In addition, the
maternal serum concentrations of pregn-
ancy-associated plasma protein (PAPP)-A
and free -human chorionic gonadotro-
phin (hCG) were determined within 10
minutes of blood collection using auto-
mated machines (DELFIA Xpress system,
PerkinElmer Life and Analytical Sciences,
Waltham, MA). Biophysical and bio-
chemical markers were combined to es-
timate the patient-specific risk for tri-
somies 21, 18, and 13.
1,2,14
Women were
given their estimated individual risk for
these trisomies and those considering
their risk to be high were offered CVS for
fetal karyotyping. Karyotype results, ob-
tained from genetic laboratories, and
details on pregnancy outcomes, ob-
From Harris Birthright Research Centre for
Fetal Medicine, King’s College Hospital, King’s
College (all authors), and the Department of
Fetal Medicine, University College London
Hospital, University College London (Dr
Nicolaides and Ms Syngelaki), University of
London, London, England, UK.
Received July 27, 2012; revised Aug. 9, 2012;
accepted Aug. 22, 2012.
The study was supported by a grant from the
Fetal Medicine Foundation (United Kingdom
charity number 1037116). The cost of
collection and analysis of the samples was
covered by Ariosa Diagnostics Inc, San Jose,
CA.
The authors report no conflict of interest.
Reprints not available from the authors.
0002-9378/free
© 2012 Published by Mosby, Inc.
http://dx.doi.org/10.1016/j.ajog.2012.08.033
For Editors’ Commentary, see
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374.e1 American Journal of Obstetrics & Gynecology NOVEMBER 2012