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Maternal serum vitamin D levels at 11-13 weeks of gestation in preeclampsia.
Yu CK, Ertl R, Skyfta E, Akolekar R, Nicolaides KH.
Hum Hypertens 2013;27:115-8 . pdf -
Maternal plasma cell-free fetal and maternal DNA at 11-13 weeks' gestation: relation to fetal and maternal characteristics and pregnancy outcomes.
Poon LC, Musci T, Song K, Syngelaki A, Nicolaides KH.
Fetal Diagn Ther 2013;33:215-23. pdf