Table 1.

Basic characteristics of the study participants.

	Cases (N = 474)	Controls (N = 948)	p
Socio-demographic characteristics, %
Maternal age ≥ 30 years	33.5	34.2	0.812
Urban residence	66.0	71.6	0.030
Maternal education, senior high school or above	58.9	80.7	<0.001
Maternal work, farmers	49.5	21.0	<0.001
Nulliparity	57.8	80.3	<0.001
Maternal health-related factors in the first trimester, %
Folate/iron supplements use	76.6	89.2	<0.001
Passive smoking	33.5	9.3	<0.001
Medication use	41.6	30.4	<0.001
Anemia	16.9	10.9	<0.001
Neonatal gender, male, %	52.3	49.7	0.348
Dietary diversity score, median (25th percentile, 75th percentile)	5.0 (3.0, 6.0)	6.0 (4.0, 8.0)	<0.001
Daily components intake during pregnancy, median (25th percentile, 75th percentile)
Total energy, kcal	1753.2 (1452.4, 2086.1)	1907.1 (1563.3, 2415.9)	0.001
Total zinc, mg	5.1 (3.2, 7.3)	7.2 (5.1, 10.9)	<0.001
Dietary zinc, mg	4.7 (3.1, 6.8)	6.4 (4.6, 9.1)	<0.001
Total copper, mg	1.6 (1.1, 2.1)	2.0 (1.4, 2.7)	<0.001
Dietary copper, mg	1.6 (1.1, 2.1)	1.9 (1.2, 2.5)	<0.001
Total selenium, mg	23.2 (15.4, 32.8)	32.5 (22.7, 46.6)	<0.001
Dietary selenium, mg	22.7 (15.1, 32.6)	30.9 (21.9, 43.7)	<0.001
Total zinc to copper ratio	3.2 (2.4, 4.4)	3.8 (3.1, 4.8)	<0.001
Dietary zinc to copper ratio	3.1 (2.4, 4.2)	3.6 (3.0, 4.5)	<0.001
Total selenium to copper ratio	14.7 (10.8, 20.7)	16.7 (13.5, 21.6)	<0.001
Dietary selenium to copper ratio	14.7 (10.8, 20.9)	17.2 (13.7, 22.7)	<0.001
Total zinc to selenium ratio	0.21 (0.18, 0.25)	0.22 (0.19, 0.27)	0.280
Dietary zinc to selenium ratio	0.21 (0.18, 0.25)	0.21 (0.18, 0.23)	0.270

Categorical variables are compared between groups by χ² test, and continuous variables are compared between groups by Mann–Whitney U test.