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How it works

Prenatal tests are usually performed to check for chromosomal conditions in babies, while in the womb.

How to take these tests?

  • During pregnancy, it is good to check ensure that your baby is safe in the womb, so discuss with your gynaecologists about Prenatal tests
  • Your gynaecologist will recommend the appropriate tests for you that will check your health as a mother and that of your baby
  • These tests include a combination of basic biochemical screening and Nuchal Translucency ultrasound scan that will be done initially
  • This combination of blood test and NT scan is done for your results to offer you better risk accessibility of a range abnormalities in your baby
  • Based on the test results, further screening or diagnostic tests will be suggested by your gynaecologist to make your diagnosis confirmatory

How are the tests done?

Prenatal screening is a safe and simple test performed using maternal blood. The screening is performed in the first trimester between 9 and 13 weeks of pregnancy.

Testing process:

A small amount of blood is drawn from the pregnant mother and tested for proteins produced by the baby inside the womb

The maternal blood samples that are collected during pregnancy is sent to the lab for a range of chromosomal risk assessment

Abnormal levels of these proteins in the sample indicates the possibility of any health risk in the baby including Down syndrome or other conditions

If the risks are high, the doctor may suggest for further invasive diagnostic tests based on the risk stated as a part of report analysis

Screening Tests

Biochemical Screening Test

Biochemical screening test is a simple screening test done by retrieving blood from the pregnant mother during the first or the second trimester.

It is very safe and detects the probable risk of chromosomal conditions in the baby by tracing the presence of certain protein that may be present in the maternal blood sample.

The basic biochemical screening includes double, triple and quad marker tests that are usually performed in the first and second trimesters.

Double Marker Screening Test

  • The Double Marker screening is performed in the first trimester between 10- 13 weeks
  • A small amount of mother’s blood is tested for 2 markers: PAPP-A and free B-hCG proteins present in it
  • The levels of these markers indicate the possibility of risk in the baby including Down syndrome & other disorders
  • Combined results of Double Marker Test and NT scan detects 85-95% of Down Syndrome in pregnancies.

Triple & Quadruple Marker Screening Tests

  • Triple and Quadruple Marker Tests are performed in the second trimester using the maternal blood samples between 15 weeks and 20 weeks
  • In case of Triple Marker Test, levels of hCG, alpha-fetoprotein (AFP), and estriol are measured to analyze the risk of birth defects
  • The only component that makes the Quad Marker distinct is the inclusion of Inhibin along with other substances in the screening test
  • Down Syndrome detection rate for Triple Marker Test is around 60 -70%, whereas in the Quad Marker Screening it is around 70-75%
cfDNA Test

cfDNA Testing also known as Non- Invasive Prenatal Testing is performed as a second level screening test, if the basic biochemical test result shows a moderate or a high risk for any chromosomal condition.

It is a safe & a non-invasive screening performed from 10 weeks of pregnancy onwards to detect Down syndrome and Edwards & Patau syndrome.

It gives precise results and poses no risk of miscarriage, since it is non-invasive and done using the maternal blood sample, hence recommended world-wide by doctors.

Uniqueness of cf-DNA

  • cfDNA uses cell-free DNA to check whether the baby is affected with a chromosomal condition, while the other screening tests estimate the level of proteins in the maternal blood
  • During pregnancy, the baby’s DNA circulates in the mother’s bloodstream and this non-invasive screening detects the DNA and screens it for the risk of any chromosomal abnormality
  • Although cfDNA cannot confirm the presence of chromosomal anomalies, the test results are comparatively more accurate and better than the other biochemical screening tests
  • It may help us to avoid the next level of invasive diagnostic procedures such as amniocentesis and chorionic villus sampling which are in-vitro samples retrieved by invasive techniques

Advantages of cfDNA

cfDNA is a revolutionary and safe test which may change the course of prenatal screening process.

  • Safe: cfDNA requires a few drops of maternal blood and does not involve samples collected through invasive methods. Thus, it is absolutely safe for the mother and the baby
  • Early Testing: cfDNA can be performed any time after the ninth week and the results are not influenced by the age of pregnancy, whereas other test can be done only after completion of 10 weeks
  • Accurate: The test results are highly reliable with better accuracy rate (99.5%) thus reduces unnecessary diagnostic tests which are invasive, thus recommended by gynaecologists widely
  • Quick Results: The test results are made available in the shortest time period of 2 weeks enabling immediate further course of action by the doctor and parent
Diagnostic Testing

QF-PCR Test (Faster, Reliable & Affordable)

Quantitative Fluorescence Polymerase Chain Reaction (QF-PCR) is a Cytogenetics diagnostic test that helps to detect chromosomal conditions in babies during pregnancy. This test is performed using the samples collected through amniocentesis or chronic villus sampling procedures.

This test is usually recommended by gynaecologists when the non-invasive screening test results show an increased risk of chromosomal abnormalities.

QF-PCR technology can detect conditions such as Down syndrome, Edwards syndrome & Patau syndrome, sex chromosome aneuploidies, microdeletions and microduplications.

QF-PCR technology is almost entirely automated to give rapid test results within a period of 2 days, thus enables parents and doctors to take a quicker decision.

QF-PCR is internationally recommended as it can effectively identify clinically significant chromosomal conditions.

Though QF-PCR is reliable, it is not a standalone test it needs to be complemented with Karyotyping, the gold standard methodology for confirmation of abnormalities.

Karyotyping

Karyotyping is performed with the amniotic fluid sample or the placental fluid sample collected from the pregnant mother.

The chromosomes present in the sample are isolated, cultured and studied under microscope to check for anomalies.

Any variation from the normal chromosomal number and structure will be reported as an abnormality while performing this test.

Karyotyping is a non-targeted test that does not limit to a particular set of conditions but checks for all microscopically visible chromosomal conditions.

Usually, Karyotyping test analysis is performed by trained specialists with years of technical expertise, thus called to be confirmatory.

It may take about 2-3 weeks to get the result since it takes time and extensive labour, to identify chromosomal conditions prenatally.

Other Tests

TORCH - Antenatal Infection Screening:

During pregnancy infection may pass from the mother to the child which can be screened used TORCH Test. It is an acronym of five infectious diseases:

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  • Toxoplasmosis
  • Other diseases (HIV, Measles, Syphilis)
  • Rubella
  • Cytomegalovirus
  • Herpes simplex

The test detects antibodies to these infections using the expectant mother’s blood. The presence of these antibodies indicates a current or recent infection. Your health care provider will initiate a treatment plan for the disease.

Haemoglobinopathy Screening

A hemoglobinopathy screening is a group of tests that identifies the inherent abnormalities in blood of the unborn baby .

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The risk of these medical conditions can be detected through Prenatal Haemoglobinopathy Screening using the mother’s blood. This will help the parents and the treating physician to monitor and take necessary medical treatment.

Pap Smear
Test

It is a routine prenatal test performed for all pregnant women to check for changes in the squamous cells of

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the cervix that may lead to cervical cancer if not diagnosed and treated it can be harmful for both the mom and the baby. This test will also check for bacterial infections which can be treated with antibiotics. Pap smear is a safe test for both mother and the baby.

Routine Prenatal
Tests

Any infection that the mother is infected with during the pregnancy can have a serious impact of the baby in the womb,

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if left undetected and treated thus as routine prenatal screening tests doctors prescribe these routine tests. These include blood grouping, Rh typing, Vit D test, Thyroid, HIV, haemoglobin test (check for anemia), VDRL (screening for syphilis) etc.

Test Reports & Interpretations

The result is based on the combination of blood test and ultrasound scan which gives 3 possibilities: low risk, intermediate risk, and high risk.

Test Inferences:

Low Risk

If your screening results of the routine prenatal test done during the first or second trimester shows a low risk, your doctor may suggest you to avoid any further screening/diagnostic tests. However, these screening tests are not confirmatory, unless a diagnostic test is done it does not mean that your baby has no risk of chromosomal conditions

Intermediate Risk

If the result indicates intermediate risk your doctor may suggest follow-on tests which aim to detect not all but only certain targeted (7 - 12) conditions, which represent 99.9% of clinically relevant conditions seen in unborn babies at this risk level. Tests recommended for intermediate risk level include cfDNA test & diagnostic tests such as QF-PCR and Karyotyping

High Risk

If the first trimester chromosomal screening test indicates high-risk, your doctor may recommend you to take diagnostic tests such as QF-PCR and Karyotyping. Both the diagnostic tests require samples collected through invasive procedures such as Amniocentesis and Chorionic Villus Sampling

Test Accuracy

How Accurate is the Screening Result?

  • Prenatal test results are reliable but may not be 100% precise in clinical practice, resulting in a small fraction of false positive cases. So if the results of your screening test pose any probability of risk in such cases, confirmatory diagnostic tests conducted can give the parent and the doctor a more definite and conclusive result.
  • The result will only tell you whether your baby is at a high, intermediate or low risk of having a certain medical condition. However, most babies screened as high risk are born healthy. It is important to understand that a high-risk test result does not equate to the presence of an abnormality but only helps the doctor and parents to discuss next level testing.