Objective: To measure serum level of 25 hydroxyvitamin D [25(OH)D] in pregnant women with pre-existing diabetes (DM) or developed gestational diabetes (GDM) in Far North Queensland (FNQ). The associations between maternal 25(OH)D and HbA1C, BMI at booking and the occurrence of labour complications were also determined.
Design, setting and participants: A prospective study was conducted which consecutively recruited 101 pregnant women who attended antenatal care in the Cairns Base Hospital from April to November 2012. All participants had a diagnosis of pre-existing DM or developed GDM, were at least in their second trimester at the time of recruitment, and did not use any form of vitamin D supplementation during the course of the pregnancy. A p value < 0.05 indicates statistical significance.
Results: A mean vitamin D concentration of 110.3 nmol/L was recorded; in non-indigenous and indigenous subjects means were 114.9 and 98.0 nmol/L. Six percent of subjects were vitamin D deficient, 12% insufficient and 81% sufficient. The average vitamin D level in this cohort with diabetes is similar to that of non-diabetic pregnant women in FNQ (p = 0.292), but significantly higher than those in the southern states regardless of diabetic status (six studies from four states were compared, all p values <0.001). Spearman correlation showed low vitamin D levels are correlated with higher Hba1c values (p = 0.012, correlation coefficient = -0.253), but not associated with high BMI (p = 0.812, correlation coefficient = 0.025). Fisher’s exact test indicated the occurrence of labour complications (p = 1.000) appeared not significantly associated with antenatal vitamin D levels.
Conclusions: The study contributes to the ongoing debate around the need for universal antenatal vitamin D screening in Australia. The possible implementation of such proposed screen appears immature at this stage, as the efficacy of the screen requires further justification by RCTs and the supplementation guidelines specific for pregnancy are still lacking.