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Gestational Diabetes Linked With Vitamin D Deficiency

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Vitamin D and Insulin Resistance

Researchers now recognize that vitamin D and its active metabolites play a role in insulin resistance and the expression of insulin resistance. It is also known that insulin resistance underpins the development of gestational diabetes, and as a result vitamin D has become recognized as an important line of research for studying gestational diabetes. If there is any time when vitamin D is important, it is during pregnancy. Insulin resistance increases during pregnancy; pregnant women have up to a threefold drop in insulin sensitivity, and vitamin D probably has a role in this, according to Dr. Anne Dornhorst.

Compounding a woman’s risk during pregnancy is the growing prevalence of vitamin D insufficiency and deficiency, especially in areas such as where I practice in London where many women are at risk because of their dark skin, their body covering, or both.

Dr. Lacroix’s findings are what we would expect. Her report highlights vitamin D’s emergence as a key to understanding insulin resistance. The next step is to assess the role of vitamin D supplementation in reducing gestational diabetes, and studies looking at this are now underway.

Dr. Dornhorst is an endocrinologist at the Imperial College Hospital and senior diabetologist at Charing Cross and Hammersmith Hospitals, all in London. She said that she had no relevant financial disclosures. Dr. Dornhorst made these comments in an interview.



BERLIN – Vitamin D deficiency during the first trimester of pregnancy linked with a significantly increased risk for the development of gestational diabetes by the second trimester in a study of 655 pregnant women.

The study results also indicated that increased insulin resistance explained the significant association between vitamin D deficiency and an increased incidence of gestational diabetes, Marilyn Lacroix said at the annual meeting of the European Association for the Study of Diabetes.

Mitchel L. Zoler/IMNG Medical Media

Marilyn Lacroix

The analysis showed that for every standard-deviation decrease in blood levels of 25-hydroxyvitamin D identified during the first trimester, women had a statistically significant 40% increased rate of having gestational diabetes during their second trimester, after adjustment for age, season of blood sampling, use of vitamin D supplements, and degree of adiposity, reported Ms. Lacroix, an endocrinology researcher at Sherbrooke (Que.) University. In the population studied, a standard-deviation reduction in blood levels of vitamin D corresponded to a drop of 19 nmol/L.

The study included 655 pregnant women aged 18 or older at 6-13 weeks’ gestation with a singleton pregnancy and no history of diabetes or gestational diabetes, miscarriage, or alcohol or drug abuse. The researchers measured each woman’s blood level of 25-hydroxyvitamin D at gestational week 6-13, and then assessed each woman for diabetes at week 24-28. During the study, 54 of the women (8%) developed gestational diabetes.

The prevalence of first-trimester vitamin D deficiency – a blood level of less than 50 nmol/L – was 26% among the 601 women who were normoglycemic during the second trimester, and 37% among women who developed gestational diabetes by the second trimester.

The analysis also showed a significantly reduced average Matsuda index (Diabetes Care 1999;22:1462-70), as well as a significantly reduced insulin secretion sensitivity index (Diabetic Medicine 2009;26:1198-1203) among patients who went on to have gestational diabetes. These reductions suggest that insulin resistance forms the link between low vitamin D levels and incident gestational diabetes, Ms. Lacroix said.

Ms. Lacroix reported that she and her associates also had no relevant financial disclosures.

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