DESIGN: Cross-sectional.
SETTING: Jakarta, Indonesia and Kuala Lumpur, Malaysia.
PARTICIPANTS: A convenience sample of 504 non-pregnant women 18-40 years.
MAIN MEASURES: Plasma 25-hydroxyvitamin D and PTH.
RESULTS: The mean 25-hydroxyvitamin D concentration was 48 nmol/l. Less than 1% of women had a 25-hydroxyvitamin D concentration indicative of vitamin D deficiency (<17.5 nmol/l); whereas, over 60% of women had a 25-hydroxyvitamin D concentration indicative of insufficiency (<50 nmol/l). We estimate that 52 nmol/l was the threshold concentration for plasma 25-hydroxyvitamin D above which no further suppression of PTH occurred. Below and above this concentration the slopes of the regression lines were -0.18 (different from 0; P=0.003) and -0.01 (P=0.775), respectively. The relation between vitamin D status and parathyroid hormone concentration did not differ between women with low, medium or high calcium intakes (P=0.611); however, even in the highest tertile of calcium intake, mean calcium intake was only 657 mg/d.
CONCLUSION: On the basis of maximal suppression of PTH we estimate an optimal 25-hydroxyvitamin D concentration of approximately 50 nmol/l. Many women had a 25-hydroxyvitamin D below this concentration and may benefit from improved vitamin D status.
METHOD: Data from 1,538 women were analyzed. At the first visit for prenatal care, the 50-gram glucose challenge test was followed by the 75-gram glucose tolerance test in those who screened positive. GDM was diagnosed based on the WHO (1999) criteria. Maternal complete blood count was obtained at the first visit, hospitalization for birth, and after birth. Receiver operator characteristic curves were generated to establish thresholds. Multivariable logistic regression analyses were performed to establish independent predictors of GDM.
RESULTS: GDM was diagnosed in 182/1,538 (11.8%). GDM was associated with hemoglobin level, hematocrit and erythrocyte count at the first visit for prenatal care only. Hemoglobin threshold at the first visit was established at 11.5 g/dl. After adjustment, high hemoglobin [AOR 1.5 (95% CI 1.0-2.1); p = 0.027] remained predictive of GDM.
CONCLUSIONS: High maternal hemoglobin level at the first prenatal visit is independently predictive of GDM.