Table 1. Participant characteristics.
| Characteristics | N (%) Total = 877 | |
| Centers | ||
| Center A | 214 (24.4) | |
| Center B | 433 (49.4) | |
| Center C | 230 (26.2) | |
| Maternal age at inclusion, years | ||
| 18–24 | 39 (4.5) | |
| 25–34 | 544 (62.0) | |
| ≥35 | 294 (33.5) | |
| Body mass index, kg/m2 | ||
| <18.5 | 67 (7.7) | |
| 18.5–25 | 639 (72.9) | |
| >25 | 170 (19.4) | |
| Geographic origin | ||
| Metropolitan France | 582 (66.3) | |
| Overseas France | 16 (1.8) | |
| Europe | 52 (5.9) | |
| North Africa | 90 (10.3) | |
| Sub-Saharan Africa | 49 (5.6) | |
| Asia | 26 (3.0) | |
| Other | 62 (7.1) | |
| Single | 57 (6.5) | |
| Number of children under 18 years at home | ||
| 0 | 424 (48.3) | |
| 1 | 312 (35.6) | |
| >2 | 141 (16.1) | |
| Job associated with a higher risk of viral exposure | 467 (53.2) | |
| Work in contact with the children | 87 (9.9) | |
| Healthcare worker | 88 (10.0) | |
| Professionals in contact with the public | 401 (45.7) | |
| Seasonal flu vaccination in the previous 5 years | 131 (14.9) | |
| Primiparous | 415 (47.3) | |
| Gestational age (weeks) at inclusion | ||
| <22 | 507 (57.8) | |
| [22]–[28] | 203 (23.1) | |
| >28 | 167 (19.0) | |