Xia J, et al. - Researchers prospectively and longitudinally examined the relation of vitamin D status during early to mid-pregnancy with gestational diabetes (GDM) risk via a nested case-control study of 107 GDM cases and 214 controls within the Fetal Growth Studies-Singleton Cohort. An elevated risk of GDM was observed in correlation to maternal vitamin D deficiency as early as the first trimester of pregnancy. For women who remained deficient through the second trimester, this association intensified. For improvement in risk stratification and development of effective interventions for the primary prevention of GDM, vitamin D status assessment in early pregnancy seems clinically relevant and valuable.