VDR Variants rather than Early Pregnancy Vitamin D Concentrations Are Associated with the Risk of Gestational Diabetes: The Ma’anshan Birth Cohort (MABC) Study

Table 1

Characteristics of women included for investigating the association of vitamin D concentrations and the risk of GDM.

Variables	Total	Non-GDM ()	GDM ()
Age				<0.001
				<0.001
<25	910 (29.3)	832 (30.7)	78 (19.5)
25~30	1634 (52.5)	1438 (53.0)	196 (49.1)
30~35	434 (14.0)	351 (12.9)	83 (20.8)
≥35	132 (4.2)	90 (3.3)	42 (10.5)
Prepregnancy BMI				<0.001
				<0.001
<18.5	577 (18.6)	545 (20.1)	32 (8.0)
18.5~24	2154 (69.3)	1882 (69.4)	272 (68.2)
24~28	306 (9.8)	234 (8.6)	72 (18.0)
≥28	72 (2.3)	49 (1.8)	23 (5.8)
Gender of infant				0.797
Male	1563 (50.3)	1367 (50.4)	196 (49.1)
Female	1502 (48.3)	1309 (48.3)	193 (48.4)
Unknown	45 (1.4)	35 (1.3)	10 (2.5)
Parity				0.003
Nulliparous	2751 (88.5)	2416 (89.1)	335 (84.0)
Multiparous	359 (11.5)	295 (10.9)	64 (16.0)
Education				0.554
Primary school or below	39 (1.3)	33 (1.2)	6 (1.5)
Middle school	595 (19.1)	507 (18.7)	88 (22.1)
High school	699 (22.5)	611 (22.5)	88 (22.1)
Junior college	964 (31.0)	844 (31.1)	120 (30.1)
Undergraduate or above	813 (26.1)	716 (26.4)	97 (24.3)
Monthly income (Chinese yuan)				0.087
<1000	53 (1.7)	45 (1.7)	8 (2.0)
1000~2500	771 (24.8)	655 (24.2)	116 (29.1)
2500~4000	1338 (43.0)	1167 (43.0)	171 (42.9)
>4000	948 (30.5)	844 (31.1)	104 (26.1)
Smoking in early pregnancy				0.670
No	2982 (95.9)	2601 (95.9)	381 (95.5)
Yes	128 (4.1)	110 (4.1)	18 (4.5)
Drinking				0.764
Never	2865 (92.1)	2495 (92.0)	370 (92.7)
Occasionally	240 (7.7)	212 (7.8)	28 (7.0)
Regularly	5 (0.2)	4 (0.1)	1 (0.3)
Family history of diabetes				<0.001
No	2439 (78.4)	2155 (79.5)	284 (71.2)
Yes	255 (8.2)	198 (7.3)	57 (14.3)
Uncertain	416 (13.4)	358 (13.2)	58 (14.5)
Gestational weeks in the 1^st trimester				0.660
Season of conception				<0.001
Spring	929 (29.9)	793 (29.3)	136 (34.1)
Summer	916 (29.5)	773 (28.5)	143 (35.8)
Fall	643 (20.7)	581 (21.4)	62 (15.5)
Winter	622 (20.0)	564 (20.8)	58 (14.5)
Season in the 1^st trimester				< 0.001
Spring	713 (22.9)	630 (23.2)	83 (20.8)
Summer	1187 (38.2)	998 (36.8)	189 (47.4)
Autumn	549 (17.7)	482 (17.8)	67 (16.8)
Winter	661 (21.3)	601 (22.2)	60 (15.0)
Serum 25[OH] D				<0.001
				0.002
Deficiency	2052 (66.0)	1819 (67.1)	233 (58.4)
Insufficiency	747 (24.0)	635 (23.4)	112 (28.1)
Normal	311 (10.0)	257 (9.5)	54 (13.5)
Fasting glucose				<0.001
1 h glucose load				<0.001
2 h glucose load				<0.001

Abbreviation: BMI, body mass index.