Why Early Screening for Chromosomal Abnormalities Should Be Routine?

Why Early Screening for Chromosomal Abnormalities Should Be Routine ?

In a country where nearly 26 million babies are born every year, it’s surprising how few expecting parents are offered one of the crucial tools of modern prenatal care: early screening for chromosomal abnormalities.

Globally, routine first-trimester screening for conditions like Down syndrome (Trisomy 21), Edwards syndrome (Trisomy 18), and Patau syndrome (Trisomy 13) has become the standard. In countries like the UK, US, and many across Europe, it’s not a question of if but when a pregnant woman is offered screening. 1,2 Yet, in India, access remains scattered, recommendations inconsistent, and awareness sorely lacking—even as the burden of chromosomal conditions remains just as real. So, what is this screening, when is it done, and more importantly, why are we not doing enough of it?

Aneuploidies refer to extra or missing chromosomes which can lead to lifelong conditions, many of them severe or life-threatening. The good news is that non-invasive, reliable screening is available as early as 11 to 13 weeks of pregnancy. This first-trimester screening typically includes two key components:

·   ​A nuchal translucency (NT) scan, an ultrasound that measures fluid at the back of the foetus’s neck

·   ​A double marker blood test, which checks two key pregnancy hormones: Free β-hCG and PAPP-A

Together, this is known as Combined First Trimester Screening (cFTS). When interpreted jointly, these two simple tests can screen up to 9 in 10 cases of Down syndrome—without the need for invasive procedures.

It’s Not Just About Age Anymore

For decades, maternal age was the key factor in deciding whether prenatal screening or diagnostic testing was offered. Women over 35 years were considered at higher risk for chromosomal conditions like Down syndrome, and younger women were often overlooked.3 This was partly due to the higher background risk associated with age and the limitations of invasive tests, which carried their own risks.

But with modern non-invasive screening methods now available, age alone is no longer a valid gatekeeper. While it’s true that the likelihood of certain aneuploidies increases with age, most babies with Down syndrome are born to women younger than 35—simply because most babies are born to these women.

Data from tertiary hospitals in India show that up to 80% of babies with Down syndrome are born to mothers under 35.4,5,6 According to the National Family Health Survey (NFHS-5), the average age of childbirth in India remains around 25 years, which makes this point even more significant.7

As a result, international and Indian guidelines now support universal aneuploidy screening, regardless of age. Various national and international gynaecology and doctor associations like FOGSI (Federation of Obstetric and Gynaecological Societies of India), ICMR (Indian Council for Medical Research), and ACOG (American College of Obstetricians and Gynaecologists) emphasize that every pregnant woman should be offered aneuploidyscreening. It is no longer acceptable to reserve testing only for older mothers.

Is only Ultrasound enough?

While the NT scan is helpful, it's only part of the story. A normal ultrasound doesn't rule out chromosomal abnormalities. On the contrary, increased NT might be due to other foetal issues, not just genetic syndromes.

Paired with a dual marker test, which is a blood based biochemical test, the combination significantly boosts predictive power.

Table showing a comparison of the sensitivity and positive predictive values (PPV) of the tests available for aneuploidy screening in the first trimester of pregnancy

cfDNA – cell free DNA, NIPT – non invasive prenatal test

It’s worth repeating, this isn’t a diagnostic test. It’s a risk assessment—a way to decide if further testing like Non-Invasive Prenatal Testing (NIPT) or procedures like amniocentesis might be needed.

Combined First Trimester Screening as a Prenatal Screening for Every Pregnant Woman

There’s a critical misunderstanding that needs addressing: the Combined First Trimester Screening (cFTS) is not a diagnostic test. Rather, it is a risk assessment tool – a screening test.

It doesn’t say “yes” or “no”—it says, “let’s look closer.” High-risk results should be followed by NIPT, a highly accurate blood test and if necessary Chorionic Villus Sampling (CVS) or amniocentesis.

Its role is to guide the need for further, more accurate testing such as Non-Invasive Prenatal Testing (NIPT), chorionic villus sampling (CVS), or amniocentesis.

However, in many settings across India, this screening is either underused or misrepresented. Miscommunication of the results of the cFTS as definitive, can cause either undue alarm or false reassurance. This misinterpretation undermines the true value of the test and the informed decision-making it is meant to support.

Why Is It not routinely prescribed in India?

Despite its well-established clinical value and widespread international use, first-trimester aneuploidy screening remains far from routine in India. The gap stems from a complex interplay of limited awareness among both patients and healthcare providers, inconsistent implementation of screening protocols, and financial barriers that place essential tests beyond the reach of many families. In non-metropolitan settings, screening often depends solely on maternal age or ultrasound findings, omitting more accurate risk assessments like the Double Marker Test and NT scan. Moreover, the perception of these tests as optional luxury services, rather than standard prenatal care, discourages their uptake—particularly in semi-urban and rural areas where out-of-pocket costs can be prohibitive. Cultural misconceptions add a further layer of resistance, perpetuating the myth that young maternal age equates to low risk. Until these systemic issues are addressed through policy changes, public health education, and equitable access to testing, India will continue to lag in offering this vital component of prenatal care.

Disclaimer: The information provided in this article is for general educational purposes only and is not intended as medical advice. It should not be used as a substitute for professional diagnosis, consultation, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you may have regarding your health or a medical condition.

Legal Compliance Notice: The screening tests discussed in this article are intended solely for the detection of chromosomal abnormalities and not for the determination of the sex of the fetus, in compliance with the Pre-Conception and Pre-Natal Diagnostic Techniques (Prohibition of Sex Selection) Act, 1994. 

References

1. American College of Obstetricians and Gynecologists, and Society for Maternal-FetalMedicine. "Screening for fetal chromosomal abnormalities: ACOG practice bulletin, number 226." Obstetrics & Gynecology 136.4 (2020): e48-e69.es  

2. Steffensen EH , Skakkebæk A, Gadsbøll K , et al. Inclusion of sex chromosomes in non-invasive prenatal testing in Asia, Australia, Europe and the USA: a survey study. Prenat Diagn. 2023; 43(2): 144-155. https://doi.org/10.1002/pd.6322

3. Ishwar C. Verma, Meena Lall, Ratna Dua Puri, “Down Syndrome in India—Diagnosis, Screening, and Prenatal Diagnosis”, Clinics in Laboratory Medicine, Volume 32, Issue 2, 2012, Pages 231-248, ISSN 0272-2712, https://doi.org/10.1016/j.cll.2012.04.010.

4. Kaur, Amandeep; Kaur, Anupam. Assessment of Risk Factor Associated with Down Syndrome. Journal of the Pediatrics Association of India 9(1): 24-30, Jan–Mar 2020. | DOI: 10.4103/jpai.jpai_3_20 

5. Maina P Kava, Milind S Tullu, Mamta N Muranjan, K.M Girisha, Down syndrome:Clinical profile from India, Archives of Medical Research, Volume 35, Issue 1, 2004,Pages 31-35, ISSN 0188-4409, https://doi.org/10.1016/j.arcmed.2003.06.005.

6. Singh M, Shekhar C, Shri N. Changes in age at last birth and its determinants in India. Sci Rep. 2023 Jun 27;13(1):10450. doi: 10.1038/s41598-023-37370-z.     PMID: 37369774; PMCID: PMC10300096.