Re: First‐trimester combined screening for trisomy 21 with different combinations of placental growth factor, free β‐human chorionic gonadotropin and pregnancy‐associated plasma protein‐A. K. O. Kagan, M. Hoopmann, H. Abele, R. Alkier and K. Lüthgens. Ultrasound Obstet Gynecol 2012; 40: 530–535 | Publicación