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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. -
Placental expression of alpha and beta subunits of human chorionic gonadotrophin in early pregnancies with Down's syndrome.
Brizot ML, Jauniaux E, Mckie AT, Farzaneh F, Nicolaides KH.
Hum Reprod 1995;10:2506-9.