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Objective: The aim of this study was to determine the reference ranges of second trimester nasal bone length (NBL), pre-nasal thickness (PT), and PT/NBL ratios of lowrisk pregnant women in Turkish population. Material and Methods: Pregnant women of 16-28th gestational age who underwent ultrasonographic fetal screening between November 2021 and June 2022 were retrospectively analyzed. Fetuses with congenital malformations, high risk in antenatal screening tests, diagnosed with aneuploidy, and pregnant women of non-Turkish ethnic origin were excluded from the study. Fetuses were classified as =19+6 weeks, 20+0-20+6 weeks, 21+0-21+6 weeks, 22+0-22+6 weeks, 23+0-23+6 weeks, and =24+0 weeks. NBL, PT, and PT/NBL ratio was evaluated for each gestational age separately. Results: A total of 242 fetuses were included in the study. The mean NBL and mean PT increased with gestational age (6.42±0.65 at 20+0-20+6 weeks versus 7.65±0.79 at 23+0-23+6 weeks and 3.10±0.62 at 20+0-20+6 weeks vs. 3.55±0.63 at 23+0-23+6 weeks, respectively). Both NBL and PT were positively correlated with gestational age whereas the PT/NBL ratio was constant throughout the second trimester (PCC=0.81, p<0.001, PCC=0.56, p<0.001, and PCC=-0.07, p=0.255, respectively). The mean PT/NBL ratio in the second trimester was calculated as 0.46 (95% CI, 0.45-0.47, 5th p=0.35 and 95th p=0.62). Conclusion: The reference ranges for NBL, PT, and PT/NBL ratio may vary in different populations. Therefore, the use of population-specific nomograms may lead to higher success rates in Down syndrome screening. [ABSTRACT FROM AUTHOR]

Objective To assess the value of the prenasal thickness to nasal bone length ratio (PT/NBL) for detecting trisomy 21 (T21) after the first trimester. Method Two examiners blinded to fetal T21 status retrospectively measured prenasal thickness (PT) and nasal bone length (NBL) of T21 and control fetuses at 15–36 weeks’ gestational age on two-dimensional images from all T21-screening ultrasounds from November 2010 to April 2013. ROC curve analysis and its diagnostic values determined the best cut-off value for the ratio. Interobserver reproducibility was assessed. Results Good quality ultrasound profile images were available for 26 fetuses with T21 compared to 91 normal fetuses. The median PT/NBL ratio was 1.28 for T21 and 0.73 for control fetuses ( p < 0.0001). The PT/NBL ratio performed significantly better (AUC 0.99; 95%CI 0.97–1) than either PT (0.82; 0.73–0.91) or NBL (0.91; 0.85–0.98). The optimal PT/NBL ratio cut-off was 0.98, with a sensitivity of 88.5% [76.2–100%] and a specificity of 100%. Interobserver variability was low. Conclusion The PT/NBL ratio is a strong marker for detecting T21 in the second and third trimesters, significantly more effective than either indicator alone. [ABSTRACT FROM AUTHOR]

ABSTRACT Objectives To evaluate nasal bone length ( NBL), prenasal thickness ( PT), prenasal thickness-to-nasal bone length ( PT-NBL) ratio and prefrontal space ratio ( PFSR) as markers for Down syndrome in the second and third trimesters. Methods NBL, PT, PT-NBL ratio and PFSR were measured retrospectively in stored two-dimensional images or three-dimensional volumes (corrected to the mid-sagittal plane) of fetuses with Down syndrome, which were retrieved from the digital databases of participating units. Measurements were performed on the stored images and volumes by two experienced operators, and the values obtained were compared to our previously reported normal ranges for euploid fetuses in order to assess the detection rates for Down syndrome. Results A total of 159 fetuses with Down syndrome were included in the analysis, six of which were excluded because of inadequate available images. Median maternal age was 36.0 years and median gestational age was 23 + 1 weeks. NBL and PT were correlated with gestational age ( P < 0.001), but the PT-NBL ratio and PFSR were not. Mean NBL, PT, PT-NBL ratio and PFSR were 4.42 mm, 5.56 mm, 1.26 and 0.34, respectively. The nasal bone was absent in 23 (15.4%) cases. As a marker for Down syndrome, the PT-NBL ratio yielded the highest detection rate (86.2%), followed by PFSR (79.7%), PT (63.4%) and NBL (61.9%). All markers were abnormal in 33.6% of cases, whilst all were normal in 4.7%. At least one of the four markers was abnormal in 95.3%, and either the PT-NBL ratio or PFSR was abnormal in 93.8%. Detection rates were not related to gestational age. Conclusions The PT-NBL ratio and PFSR are robust second- and third-trimester markers for Down syndrome. Both provide high detection rates and are easy to use, as the cut-off for normality is constant throughout gestation. Copyright © 2014 ISUOG. Published by John Wiley & Sons Ltd. [ABSTRACT FROM AUTHOR]

Objective: To investigate the ratio of prenasal thickness (PT) to nasal bone length (NBL) in normal and trisomy 21 fetuses in the second and third trimester in Chinese population. Methods: The NBL and PT were measured blindly by using 3D volumes in 143 normal fetuses and 31 trisomy 21 fetuses. Results: The mean PT ( r = 0.83, p = 0.004) and NBL ( r = 0.87, p = 0.0062) both increased with the gestation age, while the PT/NBL ratio ( r = 0.12, p > 0.10) remained stable. There was significant difference between normal and trisomy 21 fetuses ( p < 0.001). If we took the 95th of the normal fetuses as the cut-off value, the detection rate was only 46%. By using ROC curve to evaluate the screening value of PT/NBL ratio, the area under receiver operating characteristic (ROC) curve was 0.88 (95% confidence interval 0.81 to 0.94, p < 0.0001). Conclusions: In Chinese population, the PT/NBL ratio is not a very strong ultrasound marker to predict trisomy 21 fetuses. However, it can be used as an ultrasound marker for Down syndrome screening during the second and third trimester of pregnancy. [ABSTRACT FROM AUTHOR]

Aim: We carried out a preliminary study to compare the nasal bone length (NBL) and biparietal diameter/NBL (BPD/NBL) ratio between the Japanese and white populations. Methods: Three hundred and fifty nine (359) singleton fetuses of healthy Japanese couples were examined from June 2004 to October 2005. NBL was measured by the strict midsagittal section. The reference range of NBL was established from cross-sectional data between 15 and 25 weeks’ gestation. Results: The success rate of obtaining reliable NBL was 93% (333/356). There were 330 fetuses (93%) available for constructing a reference range from the population. The median NBL increased from 3.2 mm at 15 weeks’ to 7.6 mm at 25 weeks’ gestation. The median of BPD/NBL ratio was 9.01. Conclusions: We demonstrated that NBL was significantly shorter and BPD/NBL was significantly greater in the Japanese population than those in the white and black populations. [ABSTRACT FROM AUTHOR]