TY - JOUR AU - Kagan, K O; Wright, D; Baker, A TI - Screening for trisomy 21 by maternal age, fetal nuchal translucency thickness, free beta-human chorionic gonadotropin and pregnancy-associated plasma protein-A JO - Ultrasound Obstet Gynecol VL - 31 PY - 2008 DO - 10.1002/uog.5331 L3 - PubMed-ID: 18461550 SP - 618 EP - 624 N1 - et al. ER -