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Maternal serum alpha-fetoprotein at 12, 22 and 32 weeks' gestation in screening for pre-eclampsia.
Bredaki FE, Mataliotakis M, Wright A, Wright D, Nicolaides KH.
Ultrasound Obstet Gynecol 2016;47:466-71. pdf -
First trimester maternal serum AFP and total hCG in aneuploidies other than trisomy 21.
Spencer K, Heath V, Flack N, Ong C, Nicolaides KH.
Prenat Diagn 2000;20:635-9.