Table 2.

Univariate and multiple regressions between 25-hydroxyvitamin D (25(OH)D) and gestational diabetes mellitus (GDM)^a (odds ratios and 95% confidence intervals). Associations according to vitamin D deficiency at inclusion (25(OH)D < 50 nmol/L) and vitamin D status during pregnancy (consistently sufficient or deficient, increasing or decreasing).

	Univariate analysis				Multiple analysis (model 1)			Multiple analysis (model 2)			Multiple analysis (model 3)
	n	OR	(95% CI)	p	OR	(95% CI)	p	OR	(95% CI)	p	OR	(95% CI)	p
					n = 739, R 2 = 0.064			n = 645, R 2 = 0.113			n = 645, R 2 = 0.130
25(OH)D sufficiency (≥50 nmol/L) at inclusion (15 GW) (ref)	745
25(OH)D < 50 nmol/L		1.6	(1.2, 2.2)	<0.01	1.6	(1.1, 2.2)	<0.01	1.4	(0.95, 2.0)	0.09	1.1	(0.69, 1.6)	0.79
					n = 730, R 2 = 0.065			n = 640, R 2 = 0.108			n = 640, R 2 = 0.127
25(OH)D consistently sufficient (ref)	736
Decreasing		1.5	(0.86, 2.7)	0.15	1.4	(0.77, 2.5)	0.29	1.3	(0.68, 2.4)	0.49	1.1	(0.60, 2.1)	0.69
Increasing		1.7	(1.2, 2.6)	<0.01	1.8	(1.2, 2.7)	<0.01	1.4	(0.87, 2.2)	0.18	1.0	(0.60, 1.7)	0.97
Consistently deficient		1.9	(1.2, 2.9)	<0.01	1.7	(1.0, 2.7)	0.04	1.3	(0.74, 2.2)	0.39	0.88	(0.49, 1.6)	0.68

^aLogistic regression analysis with GDM as dependent variable. ref: referent value; GW: gestational week; R ²: coefficient of determination. Model 1: adjusted for age, parity, education, and season. Model 2: the same as model 1, with additional adjustment for the sum of skinfolds at visit 1 and change in skinfolds from visit 1 to visit 2. Model 3: the same as model 2, with additional adjustment for ethnicity/geographic origin. Consistently sufficient: 25(OH)D ≥ 37 nmol/L at 15 and 28 GW. Decreasing: 25(OH)D ≥ 37 nmol/L at 15 GW and <37 nmol/L at 28 GW. Increasing: 25(OH)D < 37 nmol/L at 15 GW and ≥37 nmol/L at 28 GW. Consistently deficient: 25(OH)D < 37 nmol/L at 15 and 28 GW.