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Second-trimester levels of pregnancy-associated plasma protein-A and free beta-hCG in pregnancies with trisomy 13.
Spencer K, Crossley JA, Aitken DA, Nicolaides KH.
Prenat Diagn 2005;25:358-61. -
Fetal mild hydronephrosis and chromosomal defects: relation to maternal age and gestation.
Snijders RJ, Sebire NJ, Faria M, Patel F, Nicolaides KH.
Fetal Diagn Ther 1995;10:349-55.