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Dose dependency between cigarette consumption and reduced maternal serum PAPP-A levels at 11-13(+6) weeks of gestation.
Kagan KO, Frisova V, Nicolaides KH, Spencer K.
Prenat Diagn 2007;27:849-53. -
A screening program for trisomy 21 at 10-14 weeks using fetal nuchal translucency, maternal serum free beta-human chorionic gonadotropin and pregnancy-associated plasma protein-A.
Spencer K, Souter V, Tul N, Snijders R, Nicolaides KH.
Ultrasound Obstet Gynecol 1999;13:231-7.