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Frontomaxillary facial angle in fetuses with trisomy 13 at 11 + 0 to 13 + 6 weeks.
Borenstein M, Persico N, Dagklis T, Faros E, Nicolaides KH.
Ultrasound Obstet Gynecol 2007;30:819-23. -
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.