Table 1.
Comparison of baseline characteristics and birth outcomes based on maternal influenza infection
| Parameters | Controls without influenza (n = 1,525,972) | Cases with influenza (n = 37,654) | p-value | |
|---|---|---|---|---|
| Maternal characteristics | Age, mean years ± SD | 30.41 ± 3.81 | 30.31 ± 3.85 | < 0.0001 |
| Advanced age with ≥35 years (n, %) | 213,886 (14.02) | 5188 (13.78) | 0.1882 | |
| Study year, n (%) | < 0.0001 | |||
| 2007 year | 377,086 (24.71) | 9548 (25.36) | ||
| 2008 year | 380,237 (24.92) | 7480 (19.87) | ||
| 2009 year | 372,847 (24.43) | 7946 (21.10) | ||
| 2010 year | 395,802 (25.94) | 12,680 (33.68) | ||
| Pre-pregnancy HTN (n, %) | 43,443 (2.85) | 1232 (2.76) | < 0.0001 | |
| Pre-pregnancy DM (n, %) | 60,406 (3.96) | 1648 (4.38) | < 0.0001 | |
| Primiparity (n, %) | 805,385 (52.78) | 18,930 (50.27) | < 0.0001 | |
| Cesarean section (n, %) | 539,328 (35.34) | 13,680 (36.33) | < 0.0001 | |
| Birth outcomes | Neonatal sex–male (n, %) | 787,549 (51.61) | 19,428 (51.60) | 0.9585 |
| Preterm birth (n, %) | 40,798 (2.67) | 1405 (3.73) | < 0.0001 | |
| Birth weight (kg), mean ± SD | 3.22 ± 0.49 | 3.20 ± 0.50 | < 0.0001 | |
| LBW (n, %) | 56,773 (3.72) | 1668 (4.43) | < 0.0001 | |
| Macrosomia (n, %) | 62,135 (4.07) | 1532 (4.07) | 0.9752 | |
SD standard deviation; HTN hypertension; DM diabetes mellitus; LBW low birth weight