-
Second-trimester screening for trisomy-21 using prefrontal space ratio.
Chaveeva P, Agathokleous M, Poon LC, Markova D, Nicolaides KH.
Fetal Diagn Ther 2013;34:50-5. pdf -
Femur and humerus length in trisomy 21 fetuses at 11-14 weeks of gestation.
Longo D, DeFigueiredo D, Cicero S, Sacchini C, Nicolaides KH.
Ultrasound Obstet Gynecol 2004;23:143-7.