Table 2 Rates and adjusted^a odds ratios (OR) with 95 % confidence intervals (95 % CI) for prematurity-related adverse outcomes by gestational age (GA) at birth among infants born at 35–36 weeks or 37–38 weeks, compared with 39–40 weeks, before and after the implementation of ultrasound in Sweden for pregnancy dating

 35–36

20.7

10.9 (8.97–13.1)

18.1

11.0 (8.81–13.8)

4.9

9.45 (7.39–12.1)

5.2

11.0 (8.48–14.2)

 37–38

5.6

2.88 (2.42–3.44)

4.4

2.62 (2.13–3.24)

1.3

2.49 (2.01–3.09)

1.0

2.01 (1.58–2.55)

 39–40

1.9

1.00 (ref)

1.7

1.00 (ref)

0.5

1.00 (ref)

0.5

1.00 (ref)

 35–36

40.7

4.61 (4.08–5.21)

37.9

5.25 (4.55–6.06)

24.8

2.99 (2.71–3.29)

19.8

3.02 (2.69–3.38)

 37–38

14.4

1.63 (1.48–1.80)

13.5

1.88 (1.68–2.11)

9.0

1.13 (1.06–1.22)

6.7

1.08 (0.99–1.17)

 39–40

8.8

1.00 (ref)

7.2

1.00 (ref)

7.9

1.00 (ref)

6.2

1.00 (ref)

 35–36

7.6

8.87 (6.53–12.0)

4.5

7.82 (5.10–12.0)

6.7

3.92 (3.25–4.73)

3.0

2.99 (2.24–3.99)

 37–38

2.0

2.32 (1.74–3.08)

1.4

2.41 (1.66–3.50)

2.3

1.41 (1.22–1.63)

0.8

0.83 (0.66–1.04)

 39–40

0.8

1.00 (ref)

0.5

1.00 (ref)

1.6

1.00 (ref)

0.9

1.00 (ref)

 35–36

30.6

33.1 (26.8–41.0)

17.8

35.6 (26.3–48.2)

16.2

82.6 (63.6–107)

8.6

63.6 (45.9–88.3)

 37–38

3.7

3.91 (3.09–4.95)

2.6

5.09 (3.69–7.01)

1.3

6.33 (4.76–8.42)

0.5

3.22 (2.18–4.75)

 39–40

0.9

1.00 (ref)

0.5

1.00 (ref)

0.2

1.00 (ref)

0.1

1.00 (ref)

 35–36

49.2

6.44 (5.74–7.22)

38.0

7.18 (6.20–8.31)

100.0

7.07 (6.70–7.46)

65.3

6.50 (6.08–6.96)

 37–38

18.9

2.42 (2.21–2.66)

12.0

2.22 (1.96–2.51)

27.6

1.87 (1.79–1.95)

15.4

1.51 (1.43–1.60)

 39–40

7.8

1.00 (ref)

5.4

1.00 (ref)

14.9

1.00 (ref)

10.2

1.00 (ref)

 35–36

238.5

5.88 (5.56–6.21)

219.5

7.62 (7.14–8.13)

292.7

16.5 (15.9–17.1)

261.2

18.8 (18.0–19.6)

 37–38

113.4

2.41 (2.32–2.51)

98.5

2.97 (2.84–3.11)

53.0

2.33 (2.25–2.41)

40.9

2.39 (2.30–2.48)

 39–40

50.0

1.00 (ref)

35.2

1.00 (ref)

23.5

1.00 (ref)

17.6

1.00 (ref)