Abstract:
Objective To establish the reference ranges of fetal prenasal thickness (PT) and nasal bone length (NBL) based on a Chinese population and to assess their predictive value for trisomy 21, 18, and 13 in the second trimester of pregnancy.
Methods Pregnant women who underwent ultrasound during the second trimester were included in this study. The PT and NBL were measured retrospectively in 253 normal fetuses and in 55 fetuses with trisomy 21, 18, and 13.
Results The mean PT [PT=-4.959+0.565GA-0.01GA2 (R2=0.725, P＜0.001)] and NBL [NBL (mm)=-5.656+0.761GA-0.01GA2 (R2=0.891, P＜0.001)] both increased with the gestational age, while the PT/NBL ratio (R2=0.004, P=0.376) remained stable. For the fetuses with trisomy 21, 18, and 13, 26.3% (10/38), 36.4% (4/11), and 16.7% (1/6) had a PT below the 5th percentile, and 42.1% (16/38), 36.4% (4/11), and 33.3% (2/6) had a NBL below the 5th percentile. The detection rate increased remarkably when PT/NBL ratio were used as a new marker for trisomy 21 fetuses, but not for trisomy 18 and 13 fetuses [65.8% (25/38), 45.5% (5/11), and 16.6% (1/6), respectively].
Conclusion Fetal PT/NBL ratio could be used as an effective predictive maker for trisomy 21, 18, and 13.
Key words:
Ultrasound,
Fetal,
Prenasal thickness,
Nasal bone length,
Prenatal diagnosis
Lei Liu, Xin Yang, Xiaohua Xu, Shengmou Lin, Chuqin Xiong, Lilu Nong, Zhenyu Dong, Shengli Li. Measurement of fetal prenasal thickness and nasal bone length as a screening tool for trisomy 21, 18, and 13 in the second trimester of pregancy[J]. Chinese Journal of Medical Ultrasound (Electronic Edition), 2023, 20(05): 506-510.