Table 3 Incidence rate ratios by ages 1–4 and 5–9 years

Hospital admissions

IRR

S.E.

P**

z

95%CI

IRR

S.E.

P**

z

95%CI

 Boy (vs girl)

1.22

0.10

0.014

2.47

1.04–1.44

1.38

0.19

0.017

2.38

1.06–1.80

 22–24 weeks GA (vs 31+)

2.60

0.58

<0.001

4.28

1.68–4.03

2.34

0.75

0.008

2.67

1.25–4.37

 25–26 weeks GA (vs 31+)

1.79

0.25

<0.001

4.22

1.37–2.35

1.52

0.35

0.070

1.81

0.97–2.39

 27–28 weeks GA (vs 31+)

1.38

0.16

0.007

2.69

1.09–1.74

1.51

0.31

0.046

1.99

1.01–2.27

 29–30 weeks GA (vs 31+)

1.41

0.15

0.002

3.15

1.14–1.74

1.04

0.21

0.836

0.21

0.70–1.54

 Small weight for GA (vs non-SWGA)

1.87

0.17

<0.001

6.84

1.56–2.24

1.15

0.18

0.384

0.87

0.84–1.57

 Malformation at birth (vs absence)

2.16

0.19

<0.001

8.52

1.81–2.57

1.55

0.22

0.002

3.04

1.17–2.05

 Apgar score at 5 min (difference from score 9)*

0.93

0.02

0.001

−3.40

0.89–0.97

0.94

0.05

0.187

−1.32

0.85–1.03

 Parous (vs non-parous)

1.18

0.10

0.056

1.91

1.00–1.40

0.76

0.11

0.053

−1.93

0.58–1.00

 Age of mother at birth (per 5 years from avg.)*

0.91

0.03

0.010

−2.56

0.85–0.98

1.03

0.06

0.579

0.55

0.92–1.16

 Bleeding any time in pregnancy (vs none)

1.31

0.14

0.012

2.51

1.06–1.63

1.11

0.21

0.581

0.55

0.76–1.62

 Any previous abortion up to 23rd week (vs none)

1.27

0.12

0.010

2.58

1.06–1.52

1.12

0.17

0.450

0.75

0.83–1.51

 University education grandparents (vs < university)

1.12

0.11

0.259

1.13

0.92–1.36

0.72

0.12

0.042

−2.03

0.53–0.99

 Mother is immigrant (vs native)

0.99

0.11

0.907

−0.12

0.79–1.23

0.97

0.18

0.882

−0.15

0.68–1.40

 Single/separated/divorced (vs cohabiting/married)

0.84

0.11

0.176

−1.35

0.66–1.08

0.54

0.21

0.103

−1.63

0.25–1.13

 Travel time hospital at birth (per 30 min from avg.)*

1.02

0.05

0.713

0.37

0.93–1.11

1.02

0.06

0.723

0.36

0.91–1.14

 Western health authority (vs South-Eastern)

0.73

0.08

0.002

−3.08

0.59–0.89

0.95

0.19

0.807

−0.24

0.64–1.41

 Central health authority (vs South-Eastern)

0.94

0.10

0.603

−0.52

0.76–1.17

1.10

0.22

0.642

0.46

0.74–1.62

 Northern health authority (vs South-Eastern)

0.82

0.11

0.157

−1.42

0.62–1.08

1.72

0.37

0.011

2.54

1.13–2.62

 Reference* rate per 1000 children per year

181

44

<0.001

21

112–293

60

22

<0.001

11

29–123

Outpatient visits

 Boy (vs girl)

1.15

0.06

0.015

2.43

1.03–1.28

1.28

0.10

0.001

3.34

1.11–1.48

 22–24 weeks GA (vs 31+)

3.12

0.44

<0.001

8.16

2.37–4.10

3.13

0.52

<0.001

6.82

2.26–4.35

 25–26 weeks GA (vs 31+)

1.89

0.18

<0.001

6.72

1.57–2.27

2.05

0.27

<0.001

5.52

1.59–2.65

 27–28 weeks GA (vs 31+)

1.68

0.14

<0.001

6.16

1.42–1.98

1.79

0.19

<0.001

5.43

1.45–2.20

 29–30 weeks GA (vs 31+)

1.34

0.11

<0.001

3.65

1.15–1.57

1.31

0.14

0.011

2.54

1.06–1.62

 Small weight for GA (vs non-SWGA)

1.50

0.09

<0.001

6.59

1.33–1.69

1.28

0.10

0.002

3.08

1.09–1.50

 Malformation at birth (vs absence)

1.57

0.10

<0.001

7.18

1.39–1.77

1.53

0.13

<0.001

5.03

1.30–1.81

 Apgar score at 5 min (difference from score 9)*

0.93

0.01

<0.001

−4.28

0.91–0.96

0.94

0.03

0.018

−2.36

0.89–0.99

 Parous (vs non-parous)

1.02

0.06

0.793

0.26

0.90–1.15

0.93

0.08

0.348

−0.94

0.79–1.09

 Age of mother at birth (per 5 years from avg.)*

1.00

0.02

0.946

−0.07

0.95–1.05

1.05

0.04

0.131

1.51

0.98–1.13

 Bleeding any time in pregnancy (vs none)

1.04

0.08

0.598

0.53

0.89–1.22

1.01

0.12

0.924

0.10

0.80–1.27

 Any previous abortion up to 23rd week (vs none)

1.17

0.08

0.025

2.25

1.02–1.34

1.00

0.09

0.955

0.06

0.85–1.19

 University education grandparents (vs < university)

1.09

0.08

0.211

1.25

0.95–1.25

0.82

0.07

0.022

−2.28

0.69–0.97

 Mother is immigrant (vs native)

0.89

0.07

0.111

−1.59

0.76–1.03

0.94

0.11

0.587

−0.54

0.74–1.18

 Single/separated/divorced (vs cohabiting/married)

0.98

0.10

0.873

−0.16

0.81–1.20

0.76

0.10

0.042

−2.03

0.58–0.99

 Travel time hospital at birth (per 30 min from avg.)*

0.97

0.02

0.160

−1.40

0.92–1.01

0.95

0.03

0.079

−1.75

0.89–1.01

 Western health authority (vs South-Eastern)

0.92

0.06

0.227

−1.21

0.80–1.05

1.15

0.11

0.153

1.43

0.95–1.38

 Central health authority (vs South-Eastern)

1.04

0.08

0.624

0.49

0.89–1.21

1.32

0.12

0.003

3.00

1.10–1.59

 Northern health authority (vs South-Eastern)

0.96

0.10

0.719

−0.36

0.79–1.18

1.39

0.23

0.046

1.99

1.01–1.93

 Reference rate per 1000 children per year

1133

192

<0.001

41

812–1579

502

115

<0.001

27

320–786