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

From: 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

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) % n(SD) % n(SD) %
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  
  1. Values for some characteristics may not be equal to total numbers in each group because of missing values
  2. SD standard deviation