Aims: Some studies have suggested that vitamin D deficiency is associated with an increased risk of first trimester miscarriages, others have suggested that it is associated with an increased risk of hyperinsulinism/insulin resistance and the development of gestational diabetes. Hyperinsulinism is also thought to increase miscarriages. We investigated the association between vitamin D levels and hyperinsulinism in a cohort of recurrent miscarriage patients. Methods: Patients undergoing miscarriage investigations had insulin and vitamin D levels tested. Vitamin D levels were classified as: sufficient (≥75 nmol/L), insufficient (50-74.9 nmol/L) or deficient (<50 nmol/L). Hyperinsulinism was assessed via a 75 g oral glucose tolerance test (OGTT) with insulin studies. Results: One hundred and fifty-five patients underwent the testing. Hyperinsulinism was detected in 58.3% of the vitamin D deficient group, 38.7% of the insufficient group, and 33.3% of the sufficient group (chi-square p = .034). There were no significant associations between BMI and vitamin D levels, or BMI and hyperinsulinism. Caucasians comprised 82% of the clinic, and 67% of these women had vitamin D insufficiency/deficiency. Noncaucasians comprised 18% of the clinic but 89% of these patients had vitamin D insufficiency/deficiency. Discussion: We found that insufficient or deficient vitamin D levels were significantly associated with hyperinsulinism in these patients. Vitamin D deficiency is also thought to contribute to an increased risk of adverse pregnancy outcomes including preeclampsia, preterm birth, small-for-gestational-age gestational diabetes mellitus, and miscarriages. Larger level one trials are needed to establish if increasing serum vitamin D levels prior to conception or in early pregnancy improves adverse pregnancy outcomes.
Keywords: Hyperinsulinism; insufficiency and deficiency; recurrent miscarriages; vitamin D sufficiency.