First Trimester Anomaly Scan and the Role of Biochemical Markers in the Detection of Aneuploidies

Abstract

Introduction: Early detection of chromosomal anomalies is crucial for managing pregnancy risks and enabling timely interventions. First-trimester screening, which combines NT measurement and biochemical markers, has proven effective in identifying pregnancies at risk for aneuploidies. These methods provide an opportunity for early intervention and informed decision-making in prenatal care. Aim: This study aims to evaluate the first- trimester anomaly scan and biochemical markers (β-hCG and PAPP-A) for risk assessment, correlating background risk with biochemical markers, and detecting aneuploidies and structural abnormalities in singleton pregnancies. Materials and Methods: A total of 50 singleton pregnancies were included in the study, with a mean gestational age of 13 weeks and 2 days and an average maternal age of 28.7 ± 3 years. NT measurements and maternal serum levels of β-hCG and PAPP-A were assessed during the first trimester. Follow-up scans were conducted for cases with abnormal NT measurements, and amniocentesis was offered for high-risk pregnancies to confirm the presence of chromosomal anomalies. Results: Most fetuses had NT measurements within the normal range (45 to 84 mm). Two cases showed NT measurements at the higher limit. Biochemical markers in these cases exhibited significant changes; however, follow-up scans did not reveal any significant abnormalities. Amniocentesis confirmed the absence of trisomies in these pregnancies. The aneuploidy detection rate ranged from 79% to 90%, with a 5% false positive rate, indicating the effectiveness of the combined first-trimester screening approach in detecting chromosomal
abnormalities. Conclusion: The combination of NT measurement, maternal age, and biochemical markers (β-hCG and PAPP-A) is an effective first trimester screening approach for detecting aneuploidies. This method demonstrated a high detection rate with a manageable false positive rate, supporting its clinical utility in prenatal care.