|Non-Invasive Prenatal Testing (NIPT)
Common Aneuploidy Screening from
Non-invasive prenatal testing (NIPT analyses cell-free DNA
circulating in the pregnant mother's blood. It is a new option in
prenatal screening for Down syndrome (trisomy 21) and other common
chromosomal conditions (trisomies 18 and 13), X and Y chromosome
conditions. This test can be requested for any singleton pregnancy,
including in vitro fertilization (IVF) pregnancies with egg donors.
It can now also be requested for ALL twin pregnancies (without X or
Y) conceived naturally or by IVF using the patient's own egg or a
About the Ariosa Harmony™ Prenatal
DNA from the fetus circulates in the mother's blood. Cell-free DNA
(cfDNA) results from the natural breakdown of fetal cells (presumed
to be mostly placental) and clears from the maternal system within
hours of giving birth.
During a pregnancy, cfDNA can be tested to give the most accurate
screening approach in estimating the risk of a fetus having a
common chromosome condition sometimes called a trisomy. This occurs
when there are three copies of a particular chromosome instead of
the expected two. The test looks to detect the following
- Trisomy 21 is the most common trisomy at the time of birth.
Also called Down syndrome, it is associated with moderate to severe
intellectual disabilities and may also lead to digestive disease,
congenital heart defects and other malformations.
- Trisomy 18 (Edwards syndrome) and Trisomy 13 (Patau syndrome)
are associated with a high rate of miscarriage. These babies are
born with severe brain abnormalities and often have congenital
heart defects as well as other birth defects. Most affected
individuals die before or soon after birth, and very few survive
beyond the first year of life.
- Sex chromosome conditions. The sex chromosomes (X and Y)
determine whether we are male or female. X and Y chromosome
conditions occur when there is a missing, extra, or incomplete copy
of one of the sex chromosomes. The Harmony with X, Y test can
assess risk for XXX, XYY, XXYY, XXY (Klinefelter syndrome), and a
missing X chromosome in a girl (Turner syndrome). There is
significant variability in the severity of these conditions, but
most individuals have mild, if any, physical or behavioural
features. If the mother is interested in having this optional
testing, she should talk with her healthcare provider to determine
if it is right for her. This option is not available for twin
The testing is non-invasive: it involves taking a blood sample
from the mother. The pregnancy is not put at risk of miscarriage,
or from other adverse outcomes that are associated with invasive
testing procedures such as amniocentesis.
Clinical studies have shown that the Ariosa HarmonyTM Prenatal
Test has exceptional accuracy for assessing fetal trisomy
A 'high risk' result is indicative of a high risk for a trisomy.
The test identifies in singleton pregnancies more than 99% of
fetuses with trisomy 21, 98% of fetuses with trisomy 18, and 80% of
fetuses with trisomy 13, and 96% of fetuses with Turner Syndrome. X
and Y analysis provides >99% accuracy for fetal sex. Accuracy
for detecting other sex chromosome anomalies varies by
After the test, the number of women required to have a CVS or an
amniocentesis is less than 1%.
It is important to note that if the test results show there is a
high risk that the fetus has trisomy 21, 18, 13 or sex chromosome
conditions, it does not mean that the fetus definitely has one of
these conditions, although it is highly likely. For this reason, in
the event of a 'high risk' (or positive) result, follow-up testing
by an invasive procedure is recommended.
In the same way if the test results show that there is a 'low
risk' that the fetus has trisomy 21, 18, 13 or sex chromosome
conditions, it is unlikely that the fetus has one of these
conditions. However, there is a very small risk that not all
trisomy fetuses will be detected.All results should be interpreted
by a clinician in the context of clinical and familial data.
Patients should continue with their usual scan appointments
Who can have the test?
The Ariosa HarmonyTM Prenatal Test can be ordered by healthcare
professionals for women with pregnancies of at least 10 weeks'
gestational age. The HarmonyTM Prenatal Test can now be ordered for
all IVF singleton pregnancies, including those with egg donors.
Samples from pregnant women with twins naturally conceived, or
those conceived using the patient's own egg, are also accepted.
This test does not assess risk for mosaicism, partial trisomies or
The results will be ready in approximately two weeks, at which
time most women can have their 12-week scan for a detailed
examination of the fetal anatomy, including measurement of nuchal
translucency, nasal bone and other important factors. In this
visit, patients can discuss the DNA and ultrasound results with
On the basis of the NIPT result and the ultrasound findings, a
patient can decide whether or not she wants to have an invasive
procedure (for example, CVS or amniocentesis).
There needs to be enough fetal DNA in the maternal blood to be
able to provide a result. If there is insufficient fetal DNA in the
sample (occurring in 3% of cases), another blood sample from the
mother may be required. This will be processed in the laboratory at
no extra charge.
What is the process?
Once the mother has taken an independent personal decision that
she wants to have the non-invasive prenatal test performed, she
will be asked to sign a consent form and her blood sample can be
taken from a vein in her arm.
Who carries out the analysis of the
Her sample and completed request form need to be sent to TDL
Genetics, after which they will be referred to Ariosa Diagnostics
Inc, USA. Ariosa performs the Harmony™ Prenatal Test on the DNA
extracted from her blood sample.
Will the mother need to have any other
The Ariosa HarmonyTM Prenatal Test does not provide information on
other rare chromosomal abnormalities. If the ultrasound scan shows
a high nuchal translucency or other major physical defects such as
brain abnormalities, heart abnormalities, the risk for some rare
chromosomal defects may be high. In such cases, the mother may
choose to have a CVS or an amniocentesis.
The non-invasive prenatal test does not provide information on
other physical defects such asspina bifida, or information on fetal
growth. It is therefore advisable that the mother has all the usual
ultrasound scans during her pregnancy.
Transfer of the mother's information
outside the European Union
For the purposes of carrying out the Ariosa HarmonyTM Prenatal
Test, the mother's personal information will be transferred outside
of the European Union, to the USA. Please be aware that the laws
applicable to her personal data in the USA are different from those
operating in the UK, where TDL Genetics is established.
Medlab Pathology will provide
- request forms
- patient consent form
- NIPT specific tubes
For further information, or sample taking packs, contact MLP on
1800 303 349 or Sales@medlabpathology.ie
New England Journal of
Clinical Studies Abstract Booklet pdf.
Test HCP Brochure
For more detailed information on the Ariosa Harmony™ Prenatal
Test, please visit: www.ariosadx.com
from maternal blood
|up to 2
For further information, or sample taking packs, contact MLP on
1800 303 349 or Sales@Medlabpathology.ie
Image: © Science Photo Library