Comparison of the ratio of second trimester fetal biometric measurements to fetal nasal bone length in fetuses with normal karyotype and trisomy 21

• Published in: Journal of clinical ultrasound Vol. 52; no. 4; pp. 368 - 376
• Main Authors: Dal, Yusuf, Akkuş, Fatih, Karagün, Şebnem, Coşkun, Ayhan
• Format: Journal Article
• Language: English
• Published: Hoboken, USA John Wiley & Sons, Inc 01-05-2024; Wiley Subscription Services, Inc
• Subjects: Adult; Amniocentesis; Biometrics; Biometry - methods; biparietal diameter; Diagnostic systems; Down syndrome; Down Syndrome - diagnostic imaging; Down Syndrome - embryology; Female; femur length; Fetuses; head circumference; Humans; humerus length; Karyotype; Karyotypes; nasal bone; Nasal Bone - diagnostic imaging; Nasal Bone - embryology; Pregnancy; Pregnancy Trimester, Second; Ratios; Sensitivity; Sensitivity and Specificity; Trisomy; trisomy 21; Ultrasonography, Prenatal - methods; Young Adult; biparietal diameter; femur length; humerus length; head circumference; nasal bone; trisomy 21
• ISSN: 0091-2751; 1097-0096
• DOI: 10.1002/jcu.23638

Aim
In this study, we compared the ratio of second trimester fetal biometric measurements to nasal bone length (NBL) in fetuses with normal karyotype and trisomy 21 to determine their diagnostic prognostic value.
Materials and Methods
The study included 148 pregnant women who obtained second‐trimester ultrasonographic fetal anatomy and had amniocentesis (AS) for fetal karyotyping. The fetal karyotype results divided the groups into normal and trisomy 21 fetuses. Age, obstetric history, first and/or second trimester screening test risk ratios, fetal biometric measurements, and NBL mm, median (MoM) multiples, and percentile values were recorded and compared between groups.
Results
BPD/NBL ratios above 9.26 predict trisomy 21 in fetuses with 77.6% sensitivity and 86.1% specificity (p = 0.001). HC/NBL ratios above 34.50 predict trisomy 21 in fetuses with 77.8% sensitivity and 88.8% specificity (p = 0.001). FL/NBL ratios above 6.02 predict trisomy 21 in fetuses with 69.6% sensitivity and 72.2% specificity (p = 0.001). HL/NB ratios above 6.56 predict trisomy 21 in fetuses with 95.5% sensitivity and 47.2% specificity (p = 0.001). The NBL MoM value demonstrated a high diagnostic accuracy for normal‐karyotype fetuses (p = 0.021).
Conclusion
We found that BPD/NBL, HC/NBL, FL/NBL, and HL/NBL ratios differed between fetuses with a normal karyotype and those with trisomy 21, specifically the HC/NBL ratio, which predicted trisomy 21 with good diagnostic accuracy. In identifying normal‐karyotype fetuses, the NBL MoM was highly accurate.
In our study, the ratio of fetal biometric measurements to NBL was significantly different in fetuses with trisomy 21, especially the HC/NBL ratio, which had high diagnostic accuracy. The BPD/NBL ratio was also highly accurate. We found that MoM may be more successful in determining normal‐karyotype fetuses.