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Table 2 Rates and adjusteda 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

From: Effects of ultrasound pregnancy dating on neonatal morbidity in late preterm and early term male infants: a register-based cohort study

Outcome by GA at Birth (weeks) 1973–1978 1995–2010
Male infants Female infants Male infants Female infants
Rate/1000 OR (95 % CI) Rate/1000 OR (95 % CI) Rate/1000 OR (95 % CI) Rate/1000 OR (95 % CI)
Neonatal death
 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)
Apgar score <7 at 5 min
 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)
Pneumothorax
 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)
RDSb
 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)
Other respiratory conditions
 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)
Hyperbilirubinemia
 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)
  1. a Adjusted for maternal age, parity, and level of hospital care
  2. b Respiratory distress syndrome of the newborn
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