Comparative analysis of serum 25(OH)D levels and selected biochemical parameters between pregnant mothers with and without gestational diabetes mellitus (GDM): A case-control study conducted among a selected population of pregnant mothers at a tertiary-care hospital in Sri Lanka.

Background: Hypovitaminosis D has become a warning sign for the development of gestational diabetes mellitus (GDM) with a lack of evidence related to pregnant mothers in Sri Lanka. Aim: This study was designed to compare serum 25(OH)D levels and selected biochemical parameters among a group of pregnant mothers in Sri Lanka.

Methods: A total of 172 pregnant mothers (GDM-86 and non-GDM-86) were recruited to this case-control study from prenatal clinics at Colombo South Teaching Hospital, Sri Lanka. Serum 25(OH)D, fasting plasma glucose (FPG) and fasting serum insulin (FSI) were measured using overnight maternal fasting venous blood samples. Serum 25(OH)D level < 20 ng/mL was considered as "hypovitaminosis D". SPSS version 23.0 was used in data analysis.

Results: During pregnancy, 44.2% (n = 38) of GDM and 38.4% (n = 33) of non-GDM mothers had received vitamin D supplements. Mean serum 25(OH)D concentrations between GDM and non-GDM mothers were 15.5 ± 4.5 ng/mL and 19.4 ± 5.9 ng/mL, respectively (P < 0.05). Among the participants, 84.9% of GDM and 60.5% of non-GDM mothers had serum 25(OH)D level < 20 ng/mL. FPG and HOMA-IR of GDM mothers were negatively correlated with serum 25(OH)D level (P < 0.05). Hypovitaminosis D was significantly associated with developing GDM after adjusting for family history of type 2 diabetes mellitus, maternal employment status, history of GDM, FPG, GWG at 24-28 weeks and HOMA-IR (aOR = 2.49; 95% CI: 1.083-5.762; P = 0.032).

Conclusion: Future randomized controlled trials are recommended to determine whether adequate vitamin D supplementation can effectively reduce the incidence of developing GDM.