1Snijders RIM, Noble P, Sebire N, et al. UK muhieentre project on assessment of risk of trisomy 21 by maternal age and fetal nuchal-translucency thickness at 10-14 weeks of gestation[ J]. Lancet, 1998, 352:343-356.
2Lam YH, Lee CP, Tang MYH, tion of first trimester fetal nuchal et al. Comparison and integratranslucency and second trimester maternal serum screening for fetal Downs syndrome[J]. Prenat Diagn,2002, 22:730-735.
3Sonek JD, Cicero S, Neiger R,et al. Nasal bone assessment in prenatal screening for trisomy 21 [ J ]. Am J Obstet Gynecol, 2006, 195:1219-1230.
4Cicero S, Avgidou K, Rembouskos G,et al. Nasal bone in firsttrimester screening for trisomy 21 [J]. Am J Obstet Gynecol, 2006, 195:109-114.
5Wald NJ, Watt HC, Hackshaw AK,et al. First and second trimester antenatal screening for Downs syndrome : the results of the Serum, Urine and Ultrasound Screening Study (SURUSS) [ J]. Health Techol Assess,2003, 7 : 1-77.
6Laigaard J, Spencer K, Chfistiansen M,et al. ADAM 12 as a first-trimester maternal serum marker in screening for Downs syndrome [ J]. Prenat Diagn ,2006, 26:973-979.
7Christiansen M, Sorensen TL, Norgaard-Pedersen B. Human placental lactogen is a first-trimester maternal serum marker of Downs syndrome [ J ]. Prenat Diagn ,2006, 27 : 1-5.
8Spencer K, Spencer CE, Power M, et al. Screening for chromosomal abnormalities in the first trimester using ultrasound and maternal serum biochemistry in a one-stop clinic : a review of three-year prospective experience [ J ]. Br J Obstet Gynaecol, 2003, 110 :281-286.
9Spencer K, Nicolaides KH. Screening for trisomy 21 in twins using ultrasound and maternal serum biochemistry in a one-stop clinic: a review of three-years experience [ J ]. Br J Obstet Gynaecol. 2003, 110:276-280.
10Malone FD, Canick JA, Ball RB, et al. First-trimester or second-trimester screening or both for Downs syndrome [ J ]. N Engl J Med ,2005, 353:2001-2011.
