Periconceptional folic acid supplementation and sex difference in prevention of neural tube defects and their subtypes in China: results from a large prospective cohort study

Table 1 Characteristics of subjects by periconceptional folic acid use and sex of infant

Characteristics	Male infant					Female infant
	Women with folic acid (n = 9497)		Women without folic acid (n = 6644)		P value	Women with folic acid (n = 8652)		Women without folic acid (n = 6008)		P value
	n(SD)	%	n(SD)	%	P value	n(SD)	%	n(SD)	%	P value
Age at pregnancy, years	24.5(2.5)		26.8(3.9)		< 0.001	24.5(2.4)		26.9(4.0)		< 0.001
Body mass index, kg/m²	21.2(2.0)		21.5(1.9)		< 0.001	21.2(2.0)		21.6(1.9)		< 0.001
Primiparous	9078	95.6	4211	63.4	< 0.001	8297	95.9	3758	62.5	< 0.001
Han ethnic group	9258	99.0	6544	99.2	0.123	8395	98.9	5914	99.2	0.092
Education
High school or higher	869	9.3	505	7.7	0.001	773	9.1	442	7.4	0.001
Junior high school	7219	77.4	5212	79.0		6563	77.5	4704	79.0
Primary school or lower, or unknown	1239	13.3	882	13.4		1127	13.3	811	13.6
Occupation
Farmer	8180	86.1	6058	91.2	0.000	7424	85.8	5494	91.4	< 0.001
Factory worker	944	9.9	443	6.7		836	9.7	380	6.3
Other or unknown	373	3.9	143	2.2		392	4.5	134	2.2

Values for some characteristics may not be equal to total numbers in each group because of missing values
SD standard deviation

ISSN: 1475-2891