Single-nucleotide polymorphisms in genes involved in folate metabolism or selected other metabolites and risk for gestational diabetes mellitus

Table 1 General characteristics of the women in the case and control groups, n (%)

Characteristics	GDM1	Control1	χ2	P value
	(n = 412)	(n = 412)
Delivery age (years)			15.388	< 0.001
20-30	97 (23.6)	136 (33.0)
30-35	193 (47.0)	197 (47.8)
35-44	121 (29.4)	79 (19.2)
Pre-pregnancy BMI (kg/m2)			51.509	< 0.001
< 18.5	32 (8.3)	55 (13.3)
18.5-24.0	225 (63.9)	306 (85.7)
24.0-28.0	95 (27.0)	43 (12.0)
≥ 28.0	32 (8.3)	8 (1.9)
Ethnicity
Han	352 (91.4)	385 (93.4)	1.164	0.281
Other	33 (8.6)	27 (6.6)
Education level			2.89	0.089
College school and below	102 (26.5)	88 (21.4)
Bachelor degree and above	283 (73.5)	324 (78.6)
Per capita annual household income (RMB)	7.26		0.027
< 50000	74 (21.8)	58 (16.2)
50000-100000	151 (44.5)	146 (40.9)
≥ 100000	114 (33.6)	153 (42.9)
Primiparity			15.812	< 0.001
Yes	210 (55.6)	284 (69.3)
No	168 (44.4)	126 (30.7)
History of GDM			23.798	< 0.001
Yes	33 (8.0)	4 (1.0)
No	379 (92.0)	408 (99.0)
Family history of diabetes			3.195	0.074
Yes	59 (15.2)	45 (10.9)
No	329 (84.8)	366 (89.1)
Amount of exercise			2.614	0.271
No	174 (46.6)	167 (40.9)
Some	144 (38.6)	176 (43.1)
A large amount	55 (14.7)	65 (15.9)
Staple food habit (days a week)			1.152	0.562
7	164 (44.1)	177 (43.5)
3-6	186 (50.0)	198 (48.6)
0-2	22 (5.9)	32 (7.9)
Periconceptional folic acid supplementation (day)	3.06		0.216
≥ 45	85 (22.9)	83 (20.4)
15-44	51 (13.7)	74 (18.2)
< 15	235 (63.3)	250 (61.4)
Periconceptional multiple micronutrients containing folic acid supplementation (day)	0.381		0.827
≥ 45	102 (27.5)	104 (25.6)
15-44	78 (21.0)	87 (21.4)
< 15	191 (51.5)	216 (53.1)
Overview of folic acid supplementation (day)	0.406		0.816
≥ 45	165 (44.5)	172 (42.3)
15-44	89 (24.0)	100 (24.6)
< 15	117 (31.5)	135 (33.2)

¹Some sample data were missing. Missing data in the gestational diabetes mellitus group: Delivery age 1 case (0.24%); pre-pregnancy body mass index 28 cases (6.8%); ethnicity 27 cases (6.6%); education level 27 cases (6.6%); per capita annual household income 73 cases (17.7%); primiparity 34 cases (8.3%); family history of diabetes 24 cases (5.8%); amount of exercise 39 cases (9.5%); staple food habit 40 cases (9.7%); periconceptional folic acid supplementation 41 cases (10%); periconceptional multiple micronutrients containing folic acid supplementation 41 cases (10%); and overview of folic acid supplementation 41 cases (10%). Missing data in the control group: Per capita annual household income 55 cases (13.3%); primiparity 2 cases (0.5%); family history of diabetes 1 case (0.2%); amount of exercise 4 cases (1%); staple food habit 5 cases (1.2%); periconceptional folic acid supplementation 5 cases (1.2%); periconceptional multiple micronutrients containing folic acid supplementation 5 cases (1.2%); and overview of folic acid supplementation 5 cases (1.2%).

GDM: Gestational diabetes mellitus; BMI: Body mass index.