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First trimester aneuploidy screening in the presence of a vanishing twin: implications for maternal serum markers.
Spencer K, Staboulidou I, Nicolaides KH.
Prenat Diagn 2010;30:235-40. -
First trimester prenatal diagnosis of trisomy 21 in discordant twins using fetal nuchal translucency thickness and maternal serum free beta-hCG and PAPP-A.
Spencer K, Nicolaides KH.
Prenat Diagn 2000;20:683-4.