Vitamin D Supplementation and the Effects on Glucose Metabolism During Pregnancy: A Randomized Controlled Trial

Diabetes Care
Q1
Jun 2014
Citations:112
Influential Citations:7
Interventional (Human) Studies
85
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Enhanced Details

Methods
Pregnant women aged ≥18 years with baseline plasma 25-hydroxyvitamin D (25OHD) <32 ng/mL before 20 weeks' gestation; double-blind randomized controlled trial comparing two vitamin D3 dosing regimens; 179 randomized to two arms; 24 nonrandomized with baseline 25OHD ≥32 ng/mL allocated to the LD group; primary endpoint was maternal glucose on a 75-g OGTT at 26–28 weeks; secondary endpoints included neonatal cord blood 25OHD and obstetric/neonatal outcomes; intention-to-treat analysis; conducted in Australia.
Intervention
Oral vitamin D3 supplementation started around 14 weeks gestation and continued until delivery; high-dose group received 5,000 IU daily; low-dose group received 400 IU daily; taken as a capsule daily.
Results
High-dose vitamin D3 (5,000 IU/d) started around 14 weeks' gestation did not improve maternal glucose metabolism (no difference in fasting or 2-hour OGTT glucose; GDM incidence not significantly different: 13% in LD vs 8% in HD, P=0.25). Neonatal cord blood 25OHD was higher with high-dose supplementation (HD: 46±11 ng/mL vs LD: 29±12 ng/mL; P<0.001). Post hoc analyses showed baseline 25OHD inversely related to fasting and 2-h OGTT glucose, and baseline 25OHD remained an independent predictor after adjustment. Authors conclude that HD supplementation starting around 14 weeks does not improve maternal glucose, but in women with baseline 25OHD <32 ng/mL, 5,000 IU/d is well tolerated and highly effective at preventing neonatal vitamin D deficiency.
Limitations
Not powered to detect differences in gestational diabetes mellitus; inclusion of a nonrandomized comparison group with higher baseline 25OHD may confound results; post hoc analyses; relatively small sample size with dropouts reduces power to detect modest effects; a larger trial (~760 participants) would be needed to reliably assess GDM risk reduction; generalizability may be limited to similar populations.

Abstract

OBJECTIVE Vitamin D deficiency in pregnancy is associated with an increased risk of gestational diabetes mellitus (GDM) and neonatal vitamin D deficiency. We conducted a double-blind, randomized controlled trial of low-dose (LD) versus high-dose (HD)...