1Nicolaides KH, Snijders RJ, Gosden CM, et al. Ultrasonographically detectable markers of fetal chromosomal abnormalities [ J ]. Lancet, 1992,340 : 704 -707
2Kharrat R, Yamamoto M, Roume J, et al. Karyotype and outcome of fetuses diagnosed with cystic hygroma in the first trimester in relation to nuchal translucency thickness [ J ]. Prenat Diagn, 2006,26:369-372
3Koklanaris N, Roman AS, Perle MA, et al. Isolated echogenic intracardiac foci in patients with low-risk triple screen results : assessing the risk of trisomy 21 [ J]. J Perinat Med,2005 ,33 :539-542
4Coco C, Jeanty P, Jeanty C. An isolated echogenic heart focus is not an indication for amniocentesis in 12,672 unselected patients[J].J Ultrasound Med,2004,23:489-496
5Cheng PJ, Shaw SW, Soong YK. Association of fetal choroid plexus cysts with trisomy 18 in a population previously screened by nuchal translucency thickness measurement [J]. J Soc Gynecol Investig,2006,13:280-284
6Snijders R J, Sebire NJ, Faria M, et al. Fetal mild hydronephrosis and chromosomal defects:relation to maternal age and gestation[J]. Fetal Diagn Ther, 1995,10:349-355
7Vergani P, Locatelli A, Biffi A, et al. Factors affecting the decision regarding amniocentesis in women at genetic risk because of age 35 years or older[ J]. Prenat Diagn,2002,22:769-774
8Pandya PP, Snijders RJ, Johnson S, et al. Natural history of trisomy 21 fetuses with increased nuchal translucency thickness [ J ]. Ultrasound Obstet Gynecol, 1995,5 : 381- 383
9Pandya PP, Kondylios A, Hilbert L, et al. Chromosomal defects and outcome in 1015 fetuses with increased nu- chal translucency[ J]. Ultrasound Obstet Gynecol, 1995, 5 : 15-19
10Nyberg DA, Souter VL, El-Bastawissi A, et al. Isolated sonographic markers for detection of fetal Down syndrome in the second trimester of pregnancy[ J]. J Ultrasound Med,2001,20 : 1053-1063
8Gianferrari EA,Benn PA,Dries L,et al.Absent or shortened nasal bone length and the detection of Down syndrome in second-trimester fetuses.Obstet Gynecol,2007,109(2 Pt 1):371-375.
9Vergani P,Locatelli A,Piccoli MG,et al.Best second trimester sonographic markers for the detecrion of trisomy 21.J Ultrasound Med,1999,18(7):469-473.