Objective Epidemiological studies relating maternal 25-hydroxyvitamin D
(25OHD) with gestational diabetes mellitus (GDM) and mode of delivery have
shown controversial results. We examined if maternal 25OHD status was
associated with plasma glucose concentrations, risks of GDM and caesarean
section in the Growing Up in Singapore Towards healthy Outcomes (GUSTO) study.
Methods Plasma 25OHD concentrations, fasting glucose (FG) and 2-hour
postprandial glucose (2HPPG) concentrations were measured in 940 women from a
Singapore mother-offspring cohort study at 26–28 weeks’ gestation. 25OHD
inadequacy and adequacy were defined based on concentrations of 25OHD
≤75nmol/l and >75nmol/l respectively. Mode of delivery was obtained from
hospital records. Multiple linear regression was performed to examine the
association between 25OHD status and glucose concentrations, while multiple
logistic regression was performed to examine the association of 25OHD status
with risks of GDM and caesarean section. Results In total, 388 (41.3%) women
had 25OHD inadequacy. Of these, 131 (33.8%), 155 (39.9%) and 102 (26.3%) were
Chinese, Malay and Indian respectively. After adjustment for confounders,
maternal 25OHD inadequacy was associated with higher FG concentrations (β =
0.08mmol/l, 95% Confidence Interval (CI) = 0.01, 0.14), but not 2HPPG
concentrations and risk of GDM. A trend between 25OHD inadequacy and higher
likelihood of emergency caesarean section (Odds Ratio (OR) = 1.39, 95% CI =
0.95, 2.05) was observed. On stratification by ethnicity, the association with
higher FG concentrations was significant in Malay women (β = 0.19mmol/l, 95%
CI = 0.04, 0.33), while risk of emergency caesarean section was greater in
Chinese (OR = 1.90, 95% CI = 1.06, 3.43) and Indian women (OR = 2.41, 95% CI =
1.01, 5.73). Conclusions 25OHD inadequacy is prevalent in pregnant Singaporean
women, particularly among the Malay and Indian women. This is associated with
higher FG concentrations in Malay women, and increased risk of emergency
caesarean section in Chinese and Indian women