Table 1.

Univariate analysis of influencing factors of serum vitamin D level in pregnant women.

Influencing factor	Variable	Number	Vitamin D level (nmol/L)	Statistics Z/P value
Age (yr old)	15–25	870	33.1 (24.1, 43.1)	6.588/.021∗
	25–35	2031	34.9 (24.7, 45.1)
	35–46	179	36.3 (28.7, 48.0)
BMI (kg/m2)	<18.5	704	34.6 (25.1, 44.9)	1.624/.312
	18.5–25.0	2248	37.5 (25.4, 46.6)
	≥25.0	128	35.8 (24.6, 47.2)
Gestational age (wk)	10–13	1025	32.4 (24.2, 42.6)	5.771/.029∗
	13–28	1770	33.7 (25.0, 44.8)
	28–32	285	35.1 (26.7, 47.4)
Season	Winter and spring	1198	32.3 (20.5, 40.5)	34.628/<.001∗
	Summer and autumn	1882	40.3 (27.7, 58.5)
Parity	First pregnancy	2658	36.5 (24.9, 46.8)	1.264/.387
	Non-first pregnancy	422	38.3 (25.3, 47.2)
Region strata	Rural areas	744	35.9 (24.7, 44.8)	2.492/.146
	Cities	2336	34.8 (25.3, 46.1)
Education level	Junior high school and below	847	34.6 (24.2, 44.5)	8.641/.006∗
	High school and above	2233	36.5 (25.5, 46.8)
Family monthly income per capita (RMB)	<1500	381	35.2 (24.7, 45.2)	1.853/.251
	1500–3000	1384	34.5 (23.9, 45.8)
	≥3000	1315	35.8 (25.6, 47.1)
Weekly time outdoors (hour)	<10	1852	33.9 (23.5, 43.6)	9.842/.004∗
	≥10	1228	36.7 (25.8, 46.5)
Vitamin D supplement	Yes	274	36.1 (24.9, 46.8)	28.381/<.001∗
	No	2806	33.5 (22.8, 44.7)
Folic acid supplement	Yes	2188	35.7 (25.5, 47.2)	3.286/.105
	No	892	34.4 (24.6, 45.1)
Calcium supplement	Yes	339	36.7 (26.2, 47.3)	4.967/.041∗
	No	2741	34.6 (24.3, 45.7)
Iron supplement	Yes	135	35.1 (25.5, 46.7)	2.092/.216
	No	2945	33.8 (24.2, 45.6)
Trace element supplement	Yes	189	36.2 (25.5, 47.2)	19.856/<.001∗
	No	2891	33.9 (23.3, 44.8)