BACKGROUND: Maternal vitamin D deficiency has been associated with cardiometabolic risk factors during pregnancy and adverse pregnancy outcomes including gestational diabetes mellitus (GDM). Vitamin D has well-established anti-inflammatory properties, yet the association between vitamin D and inflammation, particularly adipokines, remains unexplored in pregnancy. We investigated whether maternal 25-hydroxyvitamin D (25(OH)D) concentrations were related to cardiometabolic risk factors during pregnancy and pregnancy outcomes, and whether these relationships may be mediated by circulating adipokines.
METHODS: Serum samples were collected from 102 overweight or obese pregnant women at 12-15 weeks gestation for measurement of 25(OH)D, fasting lipids, interleukin-6, monocyte chemoattractant protein-1, and novel adipokines omentin-1, visfatin, and high-molecular-weight (HMW)-adiponectin. Fasting, 1-, and 2-hour glucose levels were measured by oral glucose tolerance tests (OGTT) at 28-weeks gestation. Pregnancy outcomes were recorded at delivery. All analyses were adjusted for maternal factors: age, BMI, parity, smoking status, and ethnicity.
RESULTS: In 102 pregnant women (age=31.9±4.5 years; BMI=30.6±6.6 kg/m2 [mean±SD]), mean 25(OH)D concentration at 12-15 weeks was 47.9±16.0 nmol/l. After adjustment for maternal factors, 25(OH)D concentrations were negatively associated with total cholesterol (p=0.02), triglycerides (p=0.01), fasting glucose (p=0.006) and 1-hour post-OGTT glucose (p=0.045), and positively associated with HMW-adiponectin (p=0.008). Higher 25(OH)D concentrations were associated with increased length of gestation (p=0.006) and reduced risk of GDM (OR(95%CI)=0.97(0.94-0.99),p=0.04). After additional adjustment for C-sections, higher 25(OH)D concentrations were associated with reduced risk of preterm birth (OR(95%CI)=0.89(0.80-0.99),p=0.03). Adding HMW-adiponectin to the models attenuated all associations except fasting glucose (p=0.03) and length of gestation (p=0.03).
CONCLUSIONS: Low first-trimester 25(OH)D concentrations were associated with increased cardiometabolic risk factors and adverse pregnancy outcomes, and most associations appeared to be mediated by HMW-adiponectin. Intervention and mechanistic studies are needed to further explore the effects of vitamin D in pregnancy, and to elucidate whether these effects are independent or modulated by circulating adipokines.