Multicenter study of first-trimester screening for trisomy 21 in 75 821 pregnancies: results and estimation of the potential impact of individual risk-orientated two-stage first-trimester screening - Nicolaides, K H; Spencer, K; Avgidou, K; Faiola, S; Falcon, O (Ultrasound Obstet Gynecol, 2005)
. Doi: 10.1002/uog.1860