• Vitamin D status and association with gestational diabetes mellitus in a pregnant cohort in Iceland.

      Magnusdottir, Kristin S; Tryggvadottir, Ellen A; Magnusdottir, Ola K; Hrolfsdottir, Laufey; Halldorsson, Thorhallur I; Birgisdottir, Bryndis E; Hreidarsdottir, Ingibjorg T; Hardardottir, Hildur; Gunnarsdottir, Ingibjorg; 1Unit for Nutrition Research, Landspitali University Hospital and Faculty of Food Science and Nutrition, University of Iceland, Reykjavik, Iceland. 2Institution of Health Science Research, University of Akureyri and Akureyri Hospital, Akureyri, Iceland. 3Centre for Fetal Programming, Department of Epidemiology Research, Statens Serum Institut, Copenhagen, Denmark. 4Department of Obstetrics and Gynecology, Landspitali University Hospital, Reykjavík, Iceland. 5Faculty of Medicine, University of Iceland, Reykjavík, Iceland. (Swedish Nutrition Foundation, 2021-03-23)
      Background: Vitamin D deficiency has been associated with an increased risk of gestational diabetes mellitus (GDM), one of the most common pregnancy complications. The vitamin D status has never previously been studied in pregnant women in Iceland. Objective: The aim of this research study was to evaluate the vitamin D status of an Icelandic cohort of pregnant women and the association between the vitamin D status and the GDM incidence. Design: Subjects included pregnant women (n = 938) who attended their first ultrasound appointment, during gestational weeks 11-14, between October 2017 and March 2018. The use of supplements containing vitamin D over the previous 3 months, height, pre-pregnancy weight, and social status were assessed using a questionnaire, and blood samples were drawn for analyzing the serum 25‑hydroxyvitamin D (25OHD) concentration. Information regarding the incidence of GDM later in pregnancy was collected from medical records. Results: The mean ± standard deviation of the serum 25OHD (S-25OHD) concentration in this cohort was 63±24 nmol/L. The proportion of women with an S-25OHD concentration of ≥ 50 nmol/L (which is considered adequate) was 70%, whereas 25% had concentrations between 30 and 49.9 nmol/L (insufficient) and 5% had concentrations < 30 nmol/L (deficient). The majority of women (n = 766, 82%) used supplements containing vitamin D on a daily basis. A gradual decrease in the proportion of women diagnosed with GDM was reported with increasing S-25OHD concentrations, going from 17.8% in the group with S-25OHD concentrations < 30 nmol/L to 12.8% in the group with S-25OHD concentrations ≥75 nmol/L; however, the association was not significant (P for trend = 0.11). Conclusion: Approximately one-third of this cohort had S-25OHD concentrations below adequate levels (< 50 nmol/L) during the first trimester of pregnancy, which may suggest that necessary action must be taken to increase their vitamin D levels. No clear association was observed between the vitamin D status and GDM in this study. Keywords: cod liver oil; gestational diabetes mellitus; nutritional status; pregnancy; supplements; vitamin D.