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Table 2 Incidence of outcomes in 23,899 pregnancies grouped according to gestational interval, stratified by age of mother at current delivery

From: Association between interpregnancy interval and adverse perinatal outcomes according to maternal age in the context of China’s two-child policy

Outcome

Total

 

IPI, n. (%)

Z

p-value

< 18 months (n = 1577)

18–23 months (n = 1385)

24–59 months (n = 9093)

60–119 months (n = 9031)

≥ 120 months (n = 2813)

Small-for-gestational age

        

All women

192 (0.8)

8 (0.5)

11 (0.8)

66 (0.7)

67 (0.7)

40 (1.4)

2.817

0.005

Maternal age, years

        

≤ 29

47 (1.0)

5 (0.6)

5 (0.9)

16 (0.7)

21 (2.2)

0 (zero)

2.816

0.005

30–34

81 (0.7)

1(0.2)

6 (0.9)

39 (0.7)

25 (0.6)

10 (2.4)

2.044

0.041

≥ 35

64 (0.8)

2 (1.9)

0(0)

11 (0.7)

21 (0.5)

30 (1.3)

1.640

0.100

Low birth weight at full term

        

All women

245 (1.0)

15 (1.0)

12 (0.9)

81 (0.9)

89 (1.0)

48 (1.7)

2.533

0.011

Maternal age, years

        

≤ 29

52 (1.1)

11 (1.3)

8 (1.4)

21 (0.9)

11 (1.2)

1 (7.1)

-0.342

0.732

30–34

8 (0.7)

3(0.5)

2(0.3)

45 (0.8)

29 (0.7)

4 (0.9)

0.921

0.357

≥ 35

110 (1.3)

1(1.0)

2(1.5)

15(1.0)

49 (1.2)

43 (1.8)

1.996

0.046

Premature birth

        

All women

1818 (7.6)

102 (6.5)

76 (5.5)

595 (6.5)

740 (8.2)

305 (10.8)

7.360

< 0.001

Maternal age, years

        

≤ 29

381 (8.2)

52 (6.1)

32 (5.5)

177 (7.8)

118 (12.4)

2 (14.3)

4.968

< 0.001

30–34

787 (7.1)

43 (6.9)

38 (5.6)

322 (6.0)

317 (8.0)

67 (15.8)

5.182

< 0.001

≥ 35

650 (7.9)

7 (6.8)

6 (4.5)

96 (6.5)

305 (7.4)

236 (9.9)

4.156

< 0.001

Adverse neonatal composite*

        

All women

262 (1.1)

11 (0.7)

10 (0.7)

93 (1.0)

110 (1.2)

38 (1.4)

2.688

0.007

Maternal age, years

        

≤ 29

48 (1.0)

3 (0.4)

4 (0.7)

21 (0.9)

19 (2.0)

1 (7.1)

3.555

< 0.001

30–34

122 (1.1)

7 (1.1)

6 (0.9)

53 (1.0)

46 (1.2)

10 (2.4)

1.478

0.140

≥ 35

92 (1.1)

1(1.0)

0(0)

19 (1.3)

45 (1.1)

27 (1.1)

0.187

0.851

  1. *Includes very low birth weight, very preterm births, severe neonatal asphyxia and deaths