The levels of 25(OH)D have been quantified in 42 insulin diabetic pregnancies (DP) through the three trimesters of pregnancy with a total of 177 determinations. In parallel we quantified this metabolite in 114 normal pregnant women (NP) and also in 116 normal controls (NC). In addition 25(OH)D was quantified in 18 (DP) and 19 (NP) at delivery in the 35-37th week of pregnancy, and ionic calcium was measured in their newborns at 24 h of life. Grouping by trimesters of gestation, the (NP) group had 25(OH)D levels similar to those of (NC) and none showed significant differences between trimesters of pregnancy. (DP) showed in all seasons lower (25(OH)D levels than (NC) but did not have differences in these levels between trimesters of pregnancy. The newborns of (DP) had lower ionic calcium levels than newborns of (NP). Eight newborns of (DP) had hypocalcemia and seven of their mothers showed 25(OH)D levels lower than 10 ng/ml. These findings suggest that lower 25(OH)D levels in (DP) can influence the neonatal hypocalcemia in their newborns.