DALI: Vitamin D and lifestyle intervention for gestational diabetes mellitus (GDM) prevention: an European multicentre, randomised trial – study protocol - Jelsma, JG; van Poppel, MN; Galjaard, S; Desoye, G; Corcoy, R; Devlieger, R; van Assche, A; Timmerman, D; Jans, G; Harreiter, J; Kautzky-Willer, A; Damm, P; Mathiesen, ER; Jensen, DM; Andersen, L; Dunne, F; Lapolla, A; Di Cianni, G; Bertolotto, A; Wender-Oegowska, E; Zawiejska, A; Blumska, K; Hill, D; Rebollo, P; Snoek, FJ; Simmons, D (BMC Pregnancy Childbirth, 2013)