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Table 3 Influenza in relation to risk of pre-eclampsia, preterm birth, small for gestational age birth, and birthweight

From: Risk of pregnancy complications and adverse birth outcomes after maternal A(H1N1)pdm09 influenza: a Norwegian population-based cohort study

  Without influenza, n = 1032 With influenza, n = 226
Pre-eclampsia
 Cases, n (%) 29 (2.8) 8 (3.5)
 Crude OR (95% CI) 1 (Ref) 1.27 (0.57, 2.81)
 Adjusted OR (95% CI)a 1 (Ref) 1.44 (0.64, 3.26)
Preterm birth
 Cases, n (%) 35 (3.4) 6 (2.7)
 Crude OR (95% CI) 1 (Ref) 0.78 (0.32, 1.87)
 Adjusted OR (95% CI)a 1 (Ref) 0.77 (0.32, 1.88)
Small for gestational age birth
 Cases, n (%) 82 (7.9) 21 (9.3)
 Crude OR (95% CI) 1 (Ref) 1.19 (0.72, 1.96)
 Adjusted OR (95% CI)a 1 (Ref) 1.35 (0.80, 2.28)
Birth weight
 10th percentile (g) 2975 2898
 Difference in 10th percentile, β (95% CI)b 1 (Ref) 22 (− 130, 174)
 50th percentile (g) 3589 3614
 Difference in 50th percentile, β (95% CI)b 1 (Ref) −4 (− 74, 67)
  1. aLogistic regression adjusted for maternal age at birth (continuous), parity (primiparous/multiparous), smoking during pregnancy (yes/no), and influenza risk group (yes/no)
  2. bQuantile regression adjusted for maternal age at birth (continuous), parity (primiparous/multiparous), smoking during pregnancy (yes/no), and influenza risk group (yes/no)