Question & Answer

During pregnancy small fragments of fetal DNA are present in maternal blood. These fragments are analyzed through maternal blood collection to detect chromosomal abnormalities in the fetus.

All pregnant women irrespective of age should be screened for the possibility that their fetus might have a chromosomal anomaly

The risk of having an affected child with Down Syndrome increases with maternal age but no mother, however young she may be is risk free!
Hence all pregnant women are advised screening for chromosomal anomalies.

Conventional NIPT focuses on detecting common chromosomal abnormalities affecting chromosomes 21,18,13, X and Y.
CHROME has a proven accuracy for detecting aneuploidies in these chromosomes. It also analyses the other chromosomes for numerical abnormalities.

All of us have 23 pairs or a total of 46 chromosomes. Aneuploidy is a change is this total number of chromosomes : either increase (47) or decrease (45).

Any of the 46 chromosomes can be involved. The commonest are increase in the number (trisomy) of 21,18 and 13. A decrease in one of the X chromosomes in females - Monosomy X is also common.

Aneuploid pregnancies may end in spontaneous miscarriage.
Affected children may present with birth defects, short stature and intellectual disability.

Trisomy 13 and 18 cause birth defects which can be detected by ultrasound. However prenatal ultrasound may be normal in a child with Trisomy 21.

Prenatal ultrasound helps to monitor the growth and well being of the fetus. A detailed ultrasound aims at detecting birth defects.
If ultrasound anomalies are present, one might require investigations other than CHROME.
Hence prenatal ultrasound ARE A MUST in all pregnancies.

a) Biochemical screening : This involves risk calculation using certain markers form maternal blood. However traditional screening is able to detect only 30% of affected children.
b) Diagnostic testing: Involves invasive testing either via amniocentesis or chorionic villous sampling. Though it confirms the presence/ absence of chromosomal aneuploidies, it is associated with a small risk of procedure related miscarriage.

Conventional NIPT tests are limited to detection of aneuploidies in select chromosomes: 21,16,13,X and Y usually at fetal fraction limit of upto 4%.
CHROME has been powered to detect aneuploidies in all 23 chromosomes and has been validated in samples with fetal fractions as low as 2%.

CHROME can be recommended as early as 9 weeks of gestation.

Yes. The test is also valid for Twin pregnancies, IVF with donor oocyte and Surrogate conceptions.

The results are reported as HIGH RISK and LOW RISK.
A HIGH RISK result needs to be confirmed via by chromosomal analysis on amniotic fluid, placental biopsy sample.
A BORDERLINE RISK result needs to be confirmed via by chromosomal analysis on amniotic fluid, placental biopsy sample .
Reasons for borderline risk may include low fetal fraction, presence of mosaicism - either maternal, placental of fetal.
LOW RISK result reduces the risk of trisomy 21 upto 99.9%.

In all cases where results indicate a HIGH or BORDERLINE RISK for fetal aneuploidy, a FISH analysis in performed on fetal sample. No additional charges apply for the same.

Maternal blood samples (10ml) are required in specialized tubes called cell-free DNA tubes..

TThe test reports are available within 5-7 days after sample arrival at the laboratory.

No in cases where results are available, the test does not need to be repeated.
However in few cases, a second sample may be needed if the quantity of fetal DNA is low.

No, CHROME only tests for numerical abnormalities (aneuploidies) in the fetus.
Genetic disorders caused by other mechanisms like single gene defects, methylation abnormalities or triplet repeat expansions are not tested via CHROME.

Usually your obstetrician or fetal medicine specialist will recommend the test for you. Alternatively you can contact us at...

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