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Table 1 Characteristics and distribution for risk factors between CHD and no CHD groupa

From: Incidence and risk factors of congenital heart disease in Qingdao: a prospective cohort study

Risk factors Total CHD n (%) No CHD n (%) χ2 value P value
Twin pregnancy
 No 63,590 582 (0.92%) 63,008(99.08%) 7.801 0.005
 Yes 1173 20(1.71%) 1153(98.29%)   
Maternal age (years)
 < 35 51,651 484(0.94%) 51,167(99.06%) 1.560 0.692
 ≥ 35 13,112 118(0.90%) 12,994(99.10%)   
BMI (kg/m2)
 < 18.5 5269 61(1.16%) 5208(98.84%) −1.162 0.245
 18.5–24.9 37,202 361(0.97%) 36,841(99.03%)   
 ≥ 25 11,603 108(0.93%) 11,495(99.07%)   
Living location
 City 40,274 424(1.05%) 39,850(98.95%) 8.334 0.004
 Countryside 15,324 120(0.78%) 15,204(99.22%)   
Assisted reproduction
 No 54,827 531(0.97%) 54,296(99.03%) 3.704 0.054
 Yes 789 13(1.65%) 776(97.25%)   
Maternal educational level
 Low 11,957 92(0.77%) 11,865(99.23%) −3.274 0.001
 Medium 40,605 409(1.01%) 40,196(98.99%)   
 High 3043 43(1.41%) 3000(98.59%)   
Dietary patterns
 Well-balanced diet 47,409 465(0.98%) 46,944(99.02%) −0.114 0.909
 Eat less meat 6440 61(0.95%) 6379(99.05%)   
 Eat less vegetables 1747 18(1.03%) 1729(98.07%)   
Husband age (years)
 < 35 38,489 395(1.03%) 38,095(98.97%) 2.892 0.089
 ≥ 35 17,081 149(0.87%) 16,932(99.13%)   
Number of previous pregnancies
 0 17,500 189(1.08%) 17,311(98.92%) −2.215 0.027
 1 20,106 201(1.00%) 19,905(99.00%)   
 > 1 18,013 153(0.85%) 17,860(99.15%)   
Fertility history
 0 26,021 288(1.11%) 25,733(98.89%) 8.615 0.003
 ≥ 1 29,598 255(0.86%) 29,343(99.14%)   
History of having a child with birth defects
 No 55,015 531(0.97%) 54,484(99.03%) 6.449 0.011
 Yes 604 12(1.99%) 592(98.01%)   
History of illness in the first trimester
 No 47,776 446(0.93%) 47,330(99.07%) 6.940 0.008
 Yes 7844 98(1.25%) 7746(98.75%)   
Family history of birth defect
 No 55,222 534(0.97%) 54,688(99.03%) 9.746 0.002
 Yes 398 10(2.51%) 388(97.49%)   
Family history of CHD
 No 55,521 537(0.97%) 54,984(99.03%) 38.012 < 0.001
 Yes 99 7(7.07%) 92(92.93%)   
History of folic acid intake
 Does not eat folic acid 3423 21(0.61%) 3402(99.39%) −2.279 0.022
 Eating folic acid 3 months before after pregnancy 37,683 364(0.97%) 37,319(99.03%)   
 Eating folic acid 6 months before and after Pregnancy 14,514 159(1.10%) 14,355(98.90%)   
History of husband smoking (cigarettes)
 0 34,101 355(1.04%) 33,746(98.96%) −1.641 0.101
 < 10 10,674 87(0.82%) 10,587(99.18%)   
 10–19 7059 68(0.96%) 6991(99.04%)   
 ≥ 20 3786 34(0.90%) 3752(99.10%)   
  1. aFor each factor, except for counts of its levels listed in the table, the rest was the count of missing data