Table 4 Unadjusted and adjusted^a odds ratio (OR) comparing estimated risks of each perinatal outcome at < 18, 18–23, 60–119, and ≥ 120 months interpregnancy intervals with estimated risks following 24–59 months intervals, stratified by maternal age at current delivery

Unadjusted

Adjusted^a

p-value^a

Unadjusted

Adjusted^a

p-value^a

Unadjusted

Adjusted^a

p-value^a

Unadjusted

Adjusted^a

p-value^a

Small-for-gestational age

All women

0.70

(0.31–1.37)

0.62 (0.28–1.28)

0.250

1.10 (0.55–1.99)

1.04

(0.53–1.93)

0.910

1.0

1.02 (0.73–1.44)

1.00

(0.69–1.43)

0.986

1.97 (1.33–2.93)

1.85

(1.11–3.05)

0.018

Maternal age, years

≤ 29

0.83

(0.27–2.12)

0.75

(0.24–1.98)

0.582

1.22 (0.40–3.14)

1.21

(0.39–3.14)

0.712

1.0

3.17 (1.65–6.19)

3.16

(1.62–6.30)

< 0.001

/

/

/

30–34

0.22

(0.01–1.01)

0.22

((0.01–1.03)

0.139

1.23

(0.46–2.69)

1.24

(0.47–2.75)

0.625

1.0

0.86

(0.51–1.42)

0.73

(0.43–1.23)

0.241

3.29

(1.54–6.37)

2.19

(1.13–4.89)

0.044

≥ 35

2.64

(0.41–10.02)

2.63

(0.40-10.27)

0.220

/

/

/

1.0

0.69

(0.34–1.48)

0.57

(0.28–1.24)

0.136

1.71

(0.88–3.58)

0.85

(0.40–1.93)

0.688

Low birth weight at full term

All women

1.07 (0.31–1.37)

1.14

(0.62–1.93)

0.658

0.97 (0.55–1.99)

0.98

(0.50–1.74)

0.945

1.0

1.11

(0.73–1.44)

0.97 (0.71–1.34)

0.829

1.93 (1.32–2.91)

1.34

(0.85–2.11)

0.208

Maternal age, years

≤ 29

1.40 (0.65–2.85)

1.30

(0.59–2.74)

0.496

1.50 (0.62–3.27)

1.55

(0.64–3.42)

0.300

1.0

1.25

(0.58–2.55)

1.20

(0.55–2.50)

0.630

8.18 (0.44–44.06)

10.42

(0.55–59.52)

0.030

30–34

0.57

(0.14–1.57)

0.61

(0.15–1.67)

0.404

0.35

(0.06–1.14)

0.37

(0.54–1.37)

0.165

1.0

0.87

(0.54–1.37)

0.77

(0.47–1.24)

0.280

1.12

(0.34–2.78)

0.89

(0.26–2.31)

0.824

≥ 35

0.96

(0.05–4.80)

0.86

(0.05–4.39)

0.888

1.48

(0.23–5.32)

1.35

(0.21–4.94)

0.697

1.0

1.18

(0.68–2.19)

1.09

(0.62–2.02)

0.784

1.80

(1.02–3.36)

1.27

(0.67–2.50)

0.478

Preterm birth

All women

0.99 (0.79–1.22)

0.98

(0.78–1.22)

0.867

0.83 (0.64–1.05)

0.82

(0.63–1.04)

0.113

1.0

1.27

(1.14–1.43)

1.28 (1.08–1.38)

0.001

1.74 (1.50–2.01)

1.52

(1.27–1.82)

< 0.001

Maternal age, years

≤ 29

0.77 (0.55–1.05)

0.90

(0.64–1.24)

0.523

0.69

(0.46-1.00)

0.75

(0.50–1.10)

0.156

1.0

1.67

(1.30–2.13)

1.50

(1.16–1.93)

0.002

1.96

(0.30–7.25)

1.34

(0.20–5.31)

0.709

30–34

1.16

(0.82–1.59)

1.19

(0.84–1.64)

0.314

0.93

(0.65–1.30)

0.96

(0.67–1.34)

0.806

1.0

1.35

(1.15–1.59)

1.21

(1.02–1.43)

0.029

2.93

(2.19–3.87)

2.17

(1.59–2.92)

< 0.001

≥ 35

1.05

(0.43–2.17)

1.01

(0.41–2.11)

0.985

0.68

(0.26–1.45)

0.65

(0.25–1.40)

0.314

1.0

1.16

(0.92–1.48)

1.06

(0.84–1.36)

0.625

1.59

(1.25–2.04)

1.17

(0.89–1.55)

0.026

Adverse neonatal Composite*

All women

0.68 (0.34–1.22)

0.70

(0.35–1.26)

0.265

0.70 (0.34–1.29)

0,71

(0.34–1.30)

0.300

1.0

1.19

(0.90–1.58)

1.08

(0.80–1.45)

0.631

1.33 (0.90–1.92)

0.96

(0.60–1.51)

0.852

Maternal age, years

≤ 29

0.38

(0.09–1.10)

0.48

(0.11–1.42)

0.237

0.74

(0.22–1.96)

0.84

(0.24–2.24)

0.753

1.0

2.17

(1.15–4.07)

1.76

(0.92–3.35)

0.085

8.18

(0.44–44.06)

4.59

(0.24–27.31)

0.165

30–34

1.14 (0.47–2.34)

1.13

(0.46–2.37)

0.758

0.90 (0.34–1.94)

0.91

(0.35–1.97)

0.827

1.0

1.17

(0.78–1.74)

1.03

(0.68–1.56)

0.873

2.41

(1.15–4.57)

1.62

(0.74–3.21)

0.194

≥ 35

0.75 0.04–3.69)

0.68

(0.04–3.41)

0.714

/

/

/

1.0

0.85

(0.51–1.50)

0.77

(0.45–1.36)

0.350

0.88 (0.49–1.62)

0.58

(0.30–1.13)

0.106