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Screening for trisomy 18 by fetal nuchal translucency and maternal serum free beta -hCG and PAPP-A at 10-14 weeks of gestation.
Tul N, Spencer K, Noble P, Chan C, Nicolaides K.
Prenat Diagn 1999;19:1035-42. -
Cardiac defects in 1st-trimester fetuses with trisomy 18.
Hyett JA, Moscoso G, Nicolaides KH.
Fetal Diagn Ther 1995;10:381-6.