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Screening for trisomy 21 by maternal age, fetal nuchal translucency thickness, free beta-human chorionic gonadotropin and pregnancy-associated plasma protein-A.
Kagan KO, Wright D, Baker A, Sahota D, Nicolaides KH.
Ultrasound Obstet Gynecol 2008;31:618-24. -
First-trimester screening for trisomy 21 by free beta-human chorionic gonadotropin and pregnancy-associated plasma protein-A: impact of maternal and pregnancy characteristics.
Kagan KO, Wright D, Spencer K, Molina FS, Nicolaides KH.
Ultrasound Obstet Gynecol 2008;31:493-50.