Objective: The first aim of this study was to assess 25-hydroxy vitamin D (25OHD) concentrations in women with type 1 diabetes (T1DM) during pregnancy, post-delivery and also foetal (cord blood) 25OHD concentrations and to examine relationships between these. The second aim of the study was to investigate potential interactions between maternal body mass index (BMI) and foetal vitamin D status. A further study aim was to examine potential relationships between maternal 25OHD and glycosylated haemoglobin (HbA1c) throughout pregnancy.
Research Design and Methods: This was an observational study of 52 pregnant controls without diabetes and 65 pregnant women with T1DM in a university teaching hospital. Maternal serum 25OHD was measured serially throughout the pregnancy and post-delivery. Cord blood 25OHD was measured at delivery. 25OHD was measured by liquid chromatography tandem mass spectrometry (LC-MS/MS).
Results: Vitamin D deficiency (25OHD <25 nmol/L) was apparent in both the T1DM subjects and controls at all 3 pregnancy trimesters. Vitamin D levels in all cord blood were <50 nmol/L. Maternal 25OHD correlated positively with cord 25OHD at all 3 trimesters in the T1DM group (p= 0.02; p<0.001; p<0.001). 25OHD levels within cord blood were significantly lower for women with diabetes classified as obese vs. normal weight at booking [normal weight BMI <25 kg/m2 vs. obese BMI >30 kg/m2 (nmol/L±SD); 19.93±11.15 vs. 13.73±4.74, p= 0.026]. In the T1DM group, HbA1c at booking was significantly negatively correlated with maternal 25OHD at all 3 trimesters (p= 0.004; p = 0.001; p= 0.05).
Conclusion: In T1DM pregnancy, low vitamin D levels persist throughout gestation and post-delivery. Cord blood vitamin D levels correlate with those of the mother, and are significantly lower in obese women than in their normal weight counterparts. Maternal vitamin D levels exhibit a significant negative relationship with HbA1c levels, supporting a potential role for this vitamin in maintaining glycaemic control.
Bibliographical noteAmcG devised this work and supervised the PhD from which this work was taken. AmcG wrote this manuscript and had the final say in its submission.
The current study is the first to measure 25OHD levels throughout pregnancy post-delivery, and in cord blood in T1DM women. The results of this study have provided evidence that, in T1DM pregnancy, low 25OHD levels persist throughout gestation and post-delivery. In addition, the study findings indicate that cord blood vitamin D levels correlate with those of the mother, and are significantly lower in obese women than in their normal weight counterparts, providing the first evidence in T1DM that maternal obesity negatively impacts transfer of vitamin D to the foetus. Maternal vitamin D levels were also found to exhibit a significant negative relationship with HbA1c levels throughout pregnancy, the first evidence supporting a role for this vitamin in maintaining gestational glycaemic control in T1DM.
The finding that vitamin D dependent processes both related to bone-health and non-bone health outcomes may be negatively impacted by maternal nutritional status and obesity in a T1DM cohort is a significant one and provides further evidence that population-based interventions aimed at reducing obesity and improving pre-pregnancy and gestational vitamin D status are needed
Author contribution percentage: 80.00%
ASJC Scopus subject areas
- Agricultural and Biological Sciences(all)
- Biochemistry, Genetics and Molecular Biology(all)