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Maternal age and adverse pregnancy outcomes: a cohort study.
Khalil A, Syngelaki A, Maiz N, Zinevich Y, Nicolaides KH.
Ultrasound Obstet Gynecol 2013;42:634-43. pdf -
Prediction of pregnancy complications by first-trimester maternal serum PAPP-A and free beta-hCG and with second-trimester uterine artery Doppler.
Spencer K, Yu CK, Cowans NJ, Otigbah C, Nicolaides KH.
Prenat Diagn 2005;25:949-53.