A STUDENT’S PERSPECTIVE: DOWN SYNDROME, ITS GENETIC INHERITANCE, KARYOTYPE AND PREVENTION

Abstract

Down syndrome (Trisomy 21) is the most common chromosomal disorder and a leading genetic cause of intellectual disability worldwide. In India, the situation is compounded by late diagnosis, limited access to universal prenatal screening, and lack of awareness regarding genetic counseling. Early detection and informed reproductive choices are essential to reduce the social, emotional, and economic impact on families. The present study deals with prenatal genetic screening & chromosomal testing perceived during the internship (first author) as important healthcare measures for prevention of the birth of Down syndrome in a family. The significant role of maternal biochemical screening, ultrasonography, NIPS, and confirmatory diagnostic tests is highlighted through a retrospective analysis of 3 high- risk pregnant women. The genetic tests included dual/quadruple biochemical markers, detailed fetal anomaly scan, NIPS (wherever possible), and confirmatory karyotype with FISH from amniotic fluid. Pre-test and post-test genetic counseling was provided to all 3 couples. Out of 3 high-risk pregnancies, advanced maternal age was in one case only & age ranged from 26-36 years. Two cases with positive dual/quadruple screening had normal karyotype on amniocentesis, highlighting the false-positive rate of screening. One case with abnormal USG [absent nasal bone, NT 4.0mm] and very high risk [1:9] in biochemical screening was confirmed as Trisomy 21 and opted for termination. None of the couples had undergone pre-conception carrier screening. Down syndrome continues to be the predominant chromosomal abnormality with ID in India. While screening tests are valuable for risk stratification, confirmatory testing by karyotype and FISH remains essential. Making universal prenatal screening mandatory, integrating genetic counseling at primary healthcare level, and ensuring affordable access to NIPS and prenatal diagnostic services are emphasized as important factors to reduce the birth prevalence and burden of Down syndrome in India..