Table 3 Prevalence of birth defects by demographic characteristics (univariate analysis)

Sex

 Female

67,809

47.38

1130

16.66(15.69–17.64)

Reference

 Male

75,305

52.62

1852

24.59(23.47–25.71)

1.49(1.38–1.60)

 Unknown

4

< 0.01

2

-

-

Residence

 Urban

47,777

33.38

985

20.62(19.33–21.90)

Reference

 Rural

95,341

66.62

1999

20.97(20.05–21.89)

1.02(0.94–1.10)

Number of births

 Singleton

139,557

97.51

2880

20.64(19.88–21.39)

Reference

 Multiple births

3561

2.49

104

29.21(23.59–34.82)

1.43(1.17–1.74)

Paternal age (years old)

 25–29

51,332

35.87

1172

22.83(21.52–24.14)

Reference

 < 20

267

0.19

12

44.94(19.51–70.37)

2.01(1.13–3.60)

 20–24

6928

4.84

235

33.92(29.58–38.26)

1.50(1.30–1.73)

 30–34

50,809

35.50

887

17.46(16.31–18.61)

0.76(0.70–0.83)

 >=35

33,782

23.60

678

20.07(18.56–21.58)

0.88(0.80–0.96)

Maternal age (years old)

 25–29

62,406

43.60

1260

20.19(19.08–21.31)

Reference

 < 20

2328

1.63

66

28.35(21.51–35.19)

1.42(1.10–1.82)

 20–24

24,523

17.13

537

21.90(20.05–23.75)

1.09(0.98–1.20)

 30–34

38,391

26.82

741

19.30(17.91–20.69)

0.96(0.87–1.05)

 >=35

15,470

10.81

380

24.56(22.09–27.03)

1.22(1.09–1.37)

Number of pregnancies (times)

 1

48,541

33.92

1043

21.49(20.18–22.79)

Reference

 2

57,947

40.49

1157

19.97(18.82–21.12)

0.93(0.85–1.01)

 3

20,995

14.67

446

21.24(19.27–23.21)

0.99(0.88–1.11)

 >=4

15,635

10.92

338

21.62(19.31–23.92)

1.01(0.89–1.14)

Parity (times)

 1

60,271

42.11

1320

21.90(20.72–23.08)

Reference

 2

75,934

53.06

1516

19.96(18.96–20.97)

0.91(0.84–0.98)

 >=3

6913

4.83

148

21.41(17.96–24.86)

0.98(0.82–1.16)

Maternal household registration

 Local

141,546

98.90

2892

20.43(19.69–21.18)

Reference

 Non-local

1572

1.10

92

58.52(46.57–70.48)

2.98(2.41–3.69)

Total

143,118

100.00

2984

20.85(20.10–21.60)