TY - JOUR AU - Kagan, K O; Wright, D; Valencia, C TI - Screening for trisomies 21, 18 and 13 by maternal age, fetal nuchal translucency, fetal heart rate, free beta-hCG and pregnancy-associated plasma protein-A JO - Hum Reprod VL - 23 PY - 2008 DO - 10.1093/humrep/den224 L3 - PubMed-ID: 18544579 SP - 1968 EP - 1975 N1 - et al. ER -