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Table 4 Characteristics of study sample by maternal HI-titer at delivery

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

  HI-titer = 5, n = 575 HI-titer ≥10, n = 201
Influenza (%) 13.2 37.8
Influenza risk group (%) 7.8 8.0
Age of mother, years (mean) 32.0 31.7
No previous births (%) 53.6 48.8
Smoking during pregnancy (%) 3.3 5.0
Use of folic acid during pregnancy (%) 69.9 69.2
Date of pregnancy start (median) Sept 29, 2009 Sept 22, 2009
Second or third trimester at start of pandemic (%)a 2.8 2.0
Days between end of pandemic and birth (mean)b 188 184
Date of birth (median) July 08, 2010 July 03, 2010
  1. aStart of pandemic defined as October 1, 2009
  2. bEnd of pandemic defined as December 31, 2009