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