Table 2 Preterm birth rate (%) by the infants’ characteristics and maternal nationality

Total

4.61

4.16

3.97

7.43

7.69

5.61

Maternal age group

 19 years or less

5.18

8.70

0.00

9.09

5.21

7.88

 20–24 years

4.06

2.88

2.45

4.55

4.90

4.94

 25–29 years

3.93

3.42

3.33

6.16

6.31

4.89

 30–34 years

4.40

3.75

3.82

7.63

8.05

5.79

 35–39 years

5.35

4.50

5.11

9.19

9.79

6.63

 40 years or more

6.77

6.56

6.05

10.31

11.01

9.52

Sex

 Male

5.19

4.48

4.36

8.28

8.56

6.24

 Female

3.99

3.82

3.54

6.55

6.79

4.95

Parity

 Primiparous

4.52

3.71

3.78

7.47

7.38

5.24

 Multiparous

4.69

4.57

4.17

7.42

7.85

6.00

Household occupation

 Farmer

4.75

4.26

8.06

6.10

0.00

4.71

 Self-employed

4.80

4.99

3.69

7.48

8.14

6.26

 Full-time worker 1

4.72

4.34

4.06

7.57

7.80

5.56

 Full-time worker 2

4.48

3.76

4.03

7.15

7.47

5.41

 Other occupations

4.66

3.02

3.46

7.72

8.17

6.07

 Unemployed

5.79

5.92

3.81

7.93

8.74

5.48

Paternal nationality

 Japan

4.61

4.38

4.21

7.16

5.36

5.20

 Korea

4.62

3.61

4.35

4.00

14.29

6.04

 China

4.35

6.06

3.84

4.00

0.00

3.01

 Philippines

4.83

0.00

0.00

7.78

6.25

9.09

 Brazil

6.06

0.00

6.45

8.16

8.21

7.69

 Other countries

4.92

4.39

3.59

8.84

8.88

5.75