Table 1. Demographic and lifestyle characteristics of NTDs cases and controls in five counties, Shanxi Province, China, 2010–2016.

Characteristic	NTDs cases (n=224)*			Controls (n=523)*		P
	Number	%		Number	%
* Values may not sum to the total numbers because of missing information for some subjects. Abbreviations: NTDs=neural tube defects; BMI=body mass index.
Maternal age (years)						0.005
<25	82	37.6		253	49.3
25–29	71	32.6		161	31.4
30–34	43	19.7		71	13.8
≥35	22	10.1		28	5.5
Prepregnancy BMI (kg/m2)						<0.001
<18.5	21	9.7		50	9.7
18.5–24.9	124	57.4		364	70.8
≥25	71	32.9		100	19.5
Occupation						0.094
Farmer	169	75.4		362	69.2
Others	55	24.6		161	30.8
Education						<0.001
Primary school or lower	18	8.1		24	4.6
Junior high school	150	67.3		284	54.6
Senior high school	37	16.6		107	20.6
College or higher	18	8.1		105	20.2
Gravidity						0.004
1	88	39.6		247	47.8
2	75	33.8		186	36.0
≥3	59	26.6		84	16.2
Parity						0.323
Primiparas	120	57.1		305	61.1
Multiparas	90	42.9		194	38.9
History of birth defect-affected pregnancy						<0.001
Yes	12	5.5		5	1.0
No	208	94.5		507	99.0
Fever or flu in early pregnancy						<0.001
Yes	84	38.7		84	16.6
No	133	61.3		421	83.4
Nausea and vomiting of pregnancy						0.001
Yes	53	24.5		73	14.2
No	163	75.5		442	85.8
Maternal alcohol consumption						0.078
Yes	23	10.3		34	6.5
No	201	89.7		487	93.5
Periconception folic acid use						0.043
Yes	129	58.1		337	65.9
No	93	41.9		174	34.1