Process evaluation of a randomised controlled trial aimed at improving health behaviours and vitamin D status during pregnancy: Implementation of the SPRING trial. - Proebstl, Simone; Vogel, Christina; Lawrence, Wendy; Strömmer, Sofia; Inskip, Hazel; Hammond, Julia; Hart, Kate; McGill, Karen; Harvey, Nicholas C.; Barker, Mary; Baird, Janis (PLoS ONE, 2025)