Poureisa Masoud, Daghighi Mohammad Hossein, Mazaheri Khameneh Ramin, Salehi Majd Sanaz
Neurosciences Research Center (NSRC), Department of Radiology, Radiotherapy and Nuclear Medicine, Tabriz University of Medical Sciences, Tabriz, Iran.
Department of Radiology, Radiotherapy and Nuclear Medicine, Tabriz University of Medical Sciences, Tabriz, Iran.
Iran J Radiol. 2015 Aug 5;12(4):e11905. doi: 10.5812/iranjradiol.11905. eCollection 2015 Oct.
Failed visualization of the fetal nasal bone (NB) by ultrasound at 11 - 14 weeks of gestation is strongly associated with chromosomal abnormalities. Meanwhile, the incidence of the absent fetal NB in normal fetuses in the first trimester in mothers of different ethnic origins differs significantly. It is, therefore, important to assess ethnic variations in the first-trimester visualization of the fetal NB before introducing this marker into routine screening programs for aneuploidy.
The objectives of this study were to determine the NB length and the prevalence of the NB absence as well as calculating the likelihood ratio (LR) for the absence of the NB in normal fetuses of Iranian women undergoing first-trimester screening for trisomy 21.
In 767 normal fetuses, the fetal profile was examined by ultrasound for the absence/presence of the NB. The NB length was also measured, and the LR for the NB absence was also determined.
The NB was absent in 2/767 (0.26%) of the fetuses. The mean length of the NB was 3.6 ± 0.69 mm for the fetuses of 11 - 14 weeks gestational age. The LR value of the absent NB was equal to 250 in the normal fetuses of the Iranian population living in the North-West provinces.
The low prevalence of the NB absence in normal fetuses in the present study is compatible with the larger size of the NB in Iranian people compared to other communities. Meanwhile, the reference range of the NB length in normal Iranian fetuses was established so that basic data could be recorded for further studies regarding the absence or presence of the NB in screening for chromosomal abnormalities (Down syndrome) within the Iranian population.
妊娠11 - 14周时超声未能显示胎儿鼻骨（NB）与染色体异常密切相关。同时，不同种族母亲孕早期正常胎儿中无鼻骨的发生率差异显著。因此，在将该指标引入非整倍体常规筛查项目之前，评估孕早期胎儿鼻骨可视化的种族差异很重要。
本研究的目的是确定伊朗妇女孕早期进行21三体筛查的正常胎儿的鼻骨长度、鼻骨缺失的患病率，并计算鼻骨缺失的似然比（LR）。
对767例正常胎儿进行超声检查，观察胎儿侧面图像中鼻骨的有无情况。测量鼻骨长度，并确定鼻骨缺失的似然比。
767例胎儿中有2例（0.26%）鼻骨缺失。孕11 - 14周胎儿的鼻骨平均长度为3.6±0.69mm。居住在西北部省份的伊朗人群正常胎儿中鼻骨缺失的似然比值等于250。
本研究中正常胎儿鼻骨缺失的低患病率与伊朗人鼻骨比其他群体更大的尺寸相符。同时，建立了伊朗正常胎儿鼻骨长度的参考范围，以便记录基础数据，用于伊朗人群染色体异常（唐氏综合征）筛查中鼻骨缺失或存在情况的进一步研究。
