Date of Award

January 2015

Document Type


Degree Name

Doctor of Philosophy (PhD)



First Advisor

Jody Ralph


Hyperglycemia during pregnancy is associated with adverse outcomes for both mother and offspring. In order to facilitate glucose delivery to the fetus, insulin resistance increases as gestation progresses which results in hyperglycemia if the mother’s body is unable to compensate by producing adequate insulin in response to these changes in glucose metabolism. Evidence suggests that calcidiol (vitamin D) influences insulin sensitivity and glucose metabolism in the non-pregnant population yet there are inconsistent findings on the effects of calcidiol on maternal glucose levels during pregnancy. A secondary analysis was completed on a de-identified data set. The original prospective study included a convenience sample of 52 nulliparous women from a community in the upper Midwestern United States. Serum vitamin D levels were obtained through laboratory measures at three predetermined points during pregnancy. Medical record abstraction provided blood glucose levels in mid-pregnancy and height and weight to calculate body mass index (BMI) at the beginning of pregnancy. Eighty-one percent of the participants had hypovitaminosis-D at some point during pregnancy and 67% had hypovitaminosis-D at all three points during pregnancy. Multiple regression analysis was completed to examine the relationship between calcidiol levels and blood glucose levels. A t-test was performed to look for a difference between two groups, those with adequate calcidiol levels and those with inadequate serum calcidiol levels. There was no evidence of a statistically significant relationship between calcidiol levels at any of the three points and the blood glucose levels when controlling for the known confounding variables of BMI and age (R square .084, .071, and .075 respectively). The high percentage of hypovitaminosis-D was believed to result in inadequate variance in this sample to show a difference, if one does exist. There was a statistically significant correlation among the three calcidiol levels (p < .05). There was a statistically significant inverse relationship between BMI and calcidiol levels in early pregnancy (p < .05) and mid-pregnancy (p < .05). These findings suggest that many women have hypovitaminosis-D in pregnancy, these levels are not improving during pregnancy, and that women with a higher BMI may need additional vitamin D during pregnancy.