ORIGINAL ARTICLE Normative curves of fetal nasal bone length for the ethnic Chinese population W.-H. Chiu • T.-H. Tung • Y.-s. Chen • W.-H. Wang • S.-M. Lee • S.-C. Horng • F.-Y. Yang Received: 18 January 2010 / Accepted: 22 June 2010 / Published online: 9 July 2010 Ó Royal Academy of Medicine in Ireland 2010 Abstract Objective The purpose of this study is to determine the association between fetal nasal bone length (NBL) and gestational age (GA), biparietal diameter (BPD) and head circumference (HC) in women undergoing prenatal assessments and Down syndrome screening. Methods Cross-sectional data were obtained from 3,003 women with singleton pregnancies who underwent a prenatal ultrasound examination at the Department of Obstetrics and Gynecology, Cheng Hsin General Hospital between August 2006 and July 2009. Results Statistical analyses involved linear regression. NBL with GA, BPD and HC as measured between 14 ?0 and 35 ?6 weeks of gestation were linearly related. Conclusions Using multiple parameters(GA, BPD and HC) to estimate NBL is more accurate than using than using GA or BPD or HC alone, as indicated by the higher pre- dictive value. Keywords Nasal bone length Á Head circumference Á Biparietal diameter Á Ultrasound Introduction In the presence of aneuploid chromosomes, Down syn- drome has a high incidence rate in newborns [1, 2]. Methods of screening for chromosome anomalies other than amniocentesis rely on the maternal age and maternal serum biochemical markers. Recently, fetal genetic ultra- sound screening has been proposed as an additional screening tool for aneuploidy [3]. Recent reports suggest that evaluating the fetal nasal bone (NB) might aid in the identification of fetuses at risk of Down syndrome. It has been reported that a high asso- ciation between Down syndrome and absent or hypoplastic fetal NB, with there being a high sensitivity, high speci- ficity and low false-positive rate for Down syndrome screening by fetal NB examination [4–7]. There have been many reports that the fetal nasal bone length (NBL) differs with ethnicity [8]. Reference ranges for the fetal NBL in Caucasian, African-American and South-American populations have been published [5, 9]. W.-H. Chiu Á W.-H. Wang Á F.-Y. Yang (&) Department of Biomedical Imaging and Radiological Sciences, School of Biomedical Science and Engineering, National Yang-Ming University, Taipei, Taiwan e-mail: fyyang@ym.edu.tw W.-H. Chiu Central Clinic and Hospital, Taipei, Taiwan W.-H. Chiu Á S.-M. Lee Department of Obstetrics and Gynecology, Chung Shan Hospital, Taipei, Taiwan W.-H. Wang Department of Orthopedics, Changhua Christian Hospital, Changhua, Taiwan W.-H. Chiu Department of Obstetrics and Gynecology, Cheng Hsin General Hospital, Taipei, Taiwan T.-H. Tung Department of Medical Research and Education, Cheng Hsin General Hospital, Taipei, Taiwan Y. Chen Division of Biotechnology, Chang Gung University, Keelung, Taiwan S.-C. Horng Department of Computer Science and Information Engineering, Chaoyang University of Technology, Wufong, Taichung, Taiwan 123 Ir J Med Sci (2011) 180:73–77 DOI 10.1007/s11845-010-0520-4