Combined Screening for Chromosomal Aneuploidies in the First Trimester: Results and Risk Assessment in an Indian Tertiary Care Population

Abstract

Background: For the early detection of chromosomal aneuploidies, first trimester combination screening (FTCS), which combines nuchal translucency (NT) ultrasonography with maternal serum free beta-human chorionic gonadotropin (free beta-hCG) and pregnancy-associated plasma protein-A (PAPP-A), is recommended worldwide. Due to the lack of population-specific data on FTCS performance and risk distribution in India, clinical practice must be guided by institution-level outcome assessments.

Objectives: to examine the biochemical marker profiles, risk stratification patterns, and screening outcome distribution in a tertiary care cohort of 1941 pregnant women receiving FTCS.

Methods: 1941 singleton pregnancies at 11+0 to 13+6 weeks of gestation were the subject of a retrospective observational study. In addition to maternal age and clinical history, the combined test protocol included NT measurement, free beta-hCG, and PAPP-A levels represented as multiples of the median (MoM). The Fetal Medicine Foundation (FMF) methodology was used for risk categorization.

Results: 1841 (94.85%) of the 1941 pregnancies were categorized as low risk. There were 33 (1.70%), 7 (0.36%), and 2 (0.10%) instances with increased risk for Trisomy 21 (T21), T18, and T13, respectively. 124 (6.39%) women were identified as having advanced maternal age (AMA). Biochemical abnormalities included low PAPP-A MoM in 12 (0.62%) instances and excessive free beta-hCG MoM in 118 (6.08%) cases. Eight instances (0.41%) had ultrasonography abnormalities, and ten cases (0.52%) were classified as intermediate risk.

Conclusion: With a high percentage of low-risk outcomes, FTCS successfully stratified chromosomal risk in the research cohort. The significance of biochemical and clinical risk factors in Indian obstetric populations is highlighted by the high rates of AMA and elevated free beta-hCG. These results emphasize the necessity of integrated counseling protocols in tertiary care settings and encourage the regular application of FTCS.