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First-trimester maternal serum matrix metalloproteinase-9 (MMP-9) and adverse pregnancy outcome.
Poon LC, Nekrasova E, Anastassopoulos P, Livanos P, Nicolaides KH.
Prenat Diagn 2009;29:553-9. -
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.