Prenatal Genetic Screening

Safe and secure diagnostic screening procedures to detect genetic abnormalities in the unborn child.

Maternal serum screening combines ultrasound measurements with the analysis of biochemical markers that aid in screening pregnancies for risks for trisomies 21, 18 and 13

Ultrasound measurements

Biochemical markers

Combined Screening

offers enhanced sensitivity towards early detection of common chromosomal abnormalities

First Trimester Screening (11-13.6 weeks)

Double Marker

Double marker offers early information about a baby's risk of having Down syndrome (Trisomy 21), Patau syndrome (Trisomy 13) and Edward syndrome (Trisomy18).

First trimester screening, also called the first trimester combined test, has two steps:

A blood test to measure levels of two pregnancy-specific substances in the mother’s blood - pregnancy - associated plasma protein-A(PAPP-A) and human chorionic gonadotropin(HCG)
An ultrasound exam to measure the size of the clear space in the tissue at the back of the baby’s neck (nuchal translucency)

First Trimester Quadruple

Parameters: PAPP-A + Free βhCG + PlGF + AFP
Risk assessment — Trisomy 21, Trisomy 18, Trisomy 13

Earlier risk assessment of other pregnancy complications like Pre-eclampsia and NTD

Detection rate without NT - 80% with 5% FPR
Detection rate with NT — 95% with 5% FPR

Penta Screening (11-13.6 weeks)

The Pentascreen maternal serum test is a first trimester screen that evaluates five maternal serum parameters to assess the risk of a baby being born with Trisomies 21, 18 and 13 and open neural tube defects. It can also predict maternal risk for early and late onset Pre-eclampsia*.

Parameters: Free βhG + PAPPA-A + AFP + PlGF + Inhibin A
Risk assessment —Trisomy 21, Trisomy 18, Trisomy 13, Pre-eclampsia and Open Neural Tube Defects (NTDs).

	Detection Rate	False Positive Rate
Trisomy 21	93%	3%
Early onset PE	96%	10%
Early onset PE	77%	10%

*PlGF is a predictive marker for early and late onset Pre-eclampsia (PE).

Second Trimester Screening (15-20.6 weeks)

Quadruple Marker

Free β-hCG, AFP, Unconjugated estriol (uE3) Inhibin-A

The Quad Screen is a second trimester screen that assesses the risk of a baby being born with Trisomies 21,18 and 13 and open neural tube defects (ONTDs)

Test	Detection Rate for Trisomy 21	False Positive Rate
Double Marker Screening	85%	4-7%
First Trimester Quadruple	95%	5%
Penta Screening without NT	93%	5%
Quadruple Screening	81%	7%

Non-Invasive Prenatal Screening (NIPS)

Noninvasive prenatal testing (NIPT) based on cell-free DNA analysis from maternal blood is a screening test for aneuploidy status for all autosomes including common chromosomal conditions like trisomy 13, trisomy 18, and trisomy 21, sex chromosome abnormalities and select microdeletion syndromes.

The American College of Obstetricians and Gynecologists (ACOG) and the Society for Maternal-Fetal Medicine (SMFM) endorse NIPT as having the highest detection rate and lowest false positive rate for the common aneuploidies regardless of maternal age or baseline risk, of all screening options.

Basic NIPS
Aneuploidies

Advanced NIPS
Aneuploidies +
microdeletion syndromes

Comprehensive NIPS
Aneuploidies +
microdeletion syndromes +
100 single gene disorders

Accurate fetal
fraction measurement

Higher than 99.9%
sensitivity and specificity in detecting fetal trisomies

Dual Technology
Massive Parallel Sequencing Targeted Capture Sequences

Can be done
from 10 weeks of Pregnancy

Higher accuracy
and lower false positive rates

Invasive Prenatal Testing

Chorionic Villus Sampling:

Chorionic Villus Sampling( CVS), is done at 10-12 weeks of pregnancy.

Why Should One Consider CVS?

You may wish to consider CVS:

If you have been identified as at high risk of having a child with a genetic disorder
If you have had a high risk result from routine screening (combined screening, double and/or nuchal translucency screening).
Previous child affected with a condition. Example: Thalassemia
The final decision about having any test in pregnancy is yours.

How Is CVS Performed?

CVS involves taking a tiny amount of the developing placenta, where it is attached to the uterus. The placenta contains tissue that is genetically identical to your baby. CVS may be performed in two ways. Most CVS are performed through the abdomen, but CVS may also be performed through the cervix (neck of the womb). It is performed under an ultrasound guidance to check the positions of both your baby and placenta within the womb.

You would be asked to sign a consent form before the procedure is carried out.

The risk of miscarriage after performing a CVS is approximately 1-2%

Amniocentesis

Amniocentesis is an invasive procedure performed around 16-18 weeks of pregnancy. In amniocentesis a small amount of amniotic fluid – the water around your baby inside your uterus (womb) is taken for testing.

Why Should One Consider Amniocentesis?

You may wish to consider amniocentesis if:

If you have a potential problem found on ultrasound scan, which may suggest chromosomal abnormality
If there is an abnormal result from your regular screening tests
If you have had a previous pregnancy terminated for a genetic condition.
Previous child affected with a genetic condition
Parents being carriers for a condition or one of the parents being affected with a condition

The final decision about having any test in pregnancy is yours.

How Is It Performed?

It is an ultrasound guided procedure. You need to have normal breakfast or lunch before the procedure. Try avoiding coffee and tea, as it leads to more movements of the fetus.

After observing the baby’s movement and position the doctor cleans the abdomen with an antiseptic. Under the guidance of ultrasound a small needle is inserted into the amniotic pocket.

This is to avoid any puncture or damage to the baby. About 20 ml of amniotic fluid is taken out. There is no anesthetic required, you will awake throughout the procedure.

You would be asked to sign a consent form before the procedure is carried out.

Tests

Rapid aneuploidy detection

QF PCR or FISH detect numerical variations in 13, 18, 21 , X & Y have short turn around times with equal sensitivity & specificity

Conventional Karyotyping

QF PCR or FISH cannot detect structural chromosomal abnormalities

Microarray

Microarray is a high resolution technology capable of detecting microdeletions / microduplication syndromes associated with ultrasound abnormalities which cannot be detected by conventional karyotyping

Clinical Exome Sequencing

Clinical exome sequencing covers clinically significant mutations - preferred when no genetic diagnosis has been established in index case

Targeted Screening

Targeted screening is performed when a known clinical disorder has been established. Technology used is decided on the etiology of the disorder - Includes Mutation/ Microdeletion /Microduplication analysis

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Health problems? Medical Queries? Send us your questions.

Does it hurt?

The pain from an amniocentesis procedure is similar to having a blood test from your arm, but there would slight cramps or period like pain during the procedure.

What Will the test tell me?

If you are having an amniocentesis for a chromosomal disorder, all chromosomes will be looked at. This means that the test may occasionally detect a problem with the chromosomes which was not expected. If the results show anything abnormal you will be told what the abnormality is and how this will affect your baby. If you are having an amniocentesis for a single gene disorder, only this will be tested for.

The risk of miscarriage after performing a Amniocentesis is approximately 1-2%.