• +977-1-4003006/7
  • info@nitapolyclinic.com.np

What is a prenatal screening test and why is it required?

  • 2023-03-23

Prenatal screening tests can identify whether your baby is more or less likely to have certain birth defects, many of which are genetic disorders

A Prenatal Screening test is a non-invasive biochemical test, a specific type of ultrasound and prenatal cell-free DNA screening test which is recommended during the first – second trimesters of pregnancy to determine if the growing baby is at an increased risk of having a genetic condition Such tests screen certain specific proteins and hormones released during pregnancy whose abnormal levels coupled with the age, weight; ethnicity, pre-existing diseases and type of pregnancy (singleton, multiple) of the expecting mother determine the combined risk of such conditions in the foetus.


The maternal marker is a non-invasive biochemical test, there are different Marker Tests which are recommended at different time points in the pregnancy.

Double Marker Test    Book Now

A Double Marker Test is a prenatal screening test done to determine the healthy development of the foetus. This test is combined with an ultrasound test and blood sample from the expecting mother. This test measures the levels of free Beta-hCG and Pregnancy Associated Plasma Protein (PAPP-A) in the blood.

  • Recommended during It can be done from 9 to 13 weeks of pregnancy but the ideal time for combined risk assessment is 10 to 13 weeks.
  • Beta-hCG is a glycoprotein hormone produced by the placenta during pregnancy. High levels of this hormone are indicative of a higher risk of Trisomy 18 (Edward Syndrome) and Trisomy 21 (Down syndrome) in the foetus.
  • PAPP A is a vital plasma protein. A low level of this plasma protein before the 14th week of gestation is indicative of an increased risk of Down syndrome.
  • The NT (Nuchal Translucency), an ultrasound marker is important component for combined trisomy 21 risk assessment.

First Trimester Quad Screen with Nuchal Translucency and Preeclampsia by Auto Delfia    Book Now

Alpha Feto Protein (AFP) (Maternal), Free Beta -hCG, PAPP – A, Placental Growth Factor (PLGF). This test is done between 9 and 13 Weeks 6 Days of pregnancy. However, the best time for this test is between 11 and 13 weeks of pregnancy.

Triple Marker Test   Book Now

A Triple Marker Test is a prenatal screening test to identify a risk of genetic disorders in the developing baby. This test measures the levels of three marker AFP, Unconjugated Estriol, β -HCG in blood, it is known as the Triple Marker test.

  • Recommended between 15-20 weeks of gestation.
  •  AFP is a protein which is produced by the fetus. If the levels of AFP are high, it indicates neural tube defects in the fetus or there can be incomplete closure of the fetus abdomen.
  • HCG hormone is produced by cells of the placenta. If the levels of HCG are low, it indicates a miscarriage or ectopic pregnancy. Whereas, if the levels of HCG are high this indicates multiple pregnancies.
  • Estriol is a form of the hormone estrogen which is present in both fetus and placenta. If the levels of estriol are low, it indicates the risk of the baby getting delivered with Down syndrome especially when the levels of AFP are low and HCG are high.

Quadruple Marker Test    Book Now

The Quadruple Marker Screening Test or Quad Test for pregnant women as this test to classify a patient as either high-risk or low-risk for chromosomal abnormalities (Down Syndrome-Trisomy 21, Edward’s Syndrome-Trisomy 18) and neural tube defects. The Quad screen looks at the three markers measured in the triple screen (Alpha-fetoprotein, Human Chorionic Gonadotropin, and Estriol) test plus one additional marker, Inhibin A.

This test is done between 14 and 22 weeks of pregnancy. However, the best time for this test is between 15 and 20 weeks of pregnancy.

  • Inhibin A is a hormone which is produced by the placenta. It is a dimer which means it has two parts. It is also sometimes referred to as DIA or dimeric inhibin A. In the 14 to 17 weeks of gestation (pregnancy), the levels of inhibin A in maternal blood slightly decrease and then rise again. Increased levels of Inhibin A indicate fetus with Down syndrome. Inhibin A enhances the sensitivity as well as the specificity in order to correctly identify cases of Down syndrome.


Most advanced Non-Invasive Pre-Natal Test (NIPT) is capable of genome-wide aneuploidy detection of the whole fetal genome (23 pairs of chromosomes). Test results with the interpretation of risk for Trisomy 13 Trisomy 18, Trisomy 21, and sex chromosome aneuplodies will be provided.

During the pregnancy, fetal cell-free DNA (cfDNA) circulates in the maternal blood which can be used for fetal aneuploidy analysis. Non-Invasive Prenatal Testing is a simple, risk-free and an accurate prenatal genetic test that can analyze the baby’s DNA to detect the risk for any genetic conditions which can help the couple make informed pregnancy decisions.

·       Safe - No risks of miscarriages and only maternal blood needed for testing

·       Can be used as early as 9 weeks of gestation

·       Validated and recommended by International Society of Prenatal Diagnosis

·       The test is accurate even at fetal fractions as low as 4%

·       Sensitivity & Specificity >99%

Who should consider NIPT?

As per medical societies, NIPT should be the first line of testing for all pregnancies irrespective of maternal age. It is recommended for the following conditions:

·       Positive Maternal Serum Marker reports

·       Advanced Maternal Age (>30 years)

·       Family history of chromosomal abnormalities

·       or previous child with a genetic abnormality

·       History of Recurrent pregnancy loss or infertility

What should you do if you have a positive screen result?

The Marker Tests are screening tests. and are not confirmatory of a possible genetic condition affecting the baby. The result is recommended for further testing for confirmation of the same. The mother may be offered the choice to undergo an invasive procedure such as a Chorionic villus sampling (CVS) from 11-13 weeks or an Amniocentesis from 15 weeks onwards along with targeted genetic testing like Karyotype or Fluorescence in situ Hybridisation (FISH). Invasive procedures carry a small risk of miscarriages (1-2%).

Confused about what tests to take at what intervals to screen for your cervical health? Call or WhatsApp 980103680/9801831090

Medically Reviewed by

Ramendra Kumar Raman, PhD, Clinical Research


Share the post

Leave Comment

Our Partners & Clients