TABLE 1.
Population characteristics in the first year of life
| Total | No antibiotics in third trimester | Antibiotics in third trimester | p-value # | |
| Infants | 296 | 262 | 34 | |
| Male | 155 (52.4) | 139 (53.1) | 16 (47.1) | 0.510 |
| Gestational age, weeks | 39.7±1.1 | 39.8±1.1 | 39.7±1.1 | 0.619 |
| Duration of any breastfeeding, weeks | 33.1±15.7 | 33.1±15.5 | 33.5±16.9 | 0.886 |
| Birth mode: Caesarean section | 85.0 (28.7) | 72 (27.5) | 13.0 (38.2) | 0.192 |
| Postnatal age at swab, days | 36.0±6.7 | 36.0±6.7 | 35.5±6.5 | 0.665 |
| Season of swab collection | 0.260 | |||
| Winter | 67 (22.6) | 62 (23.7) | 5 (14.7) | |
| Spring | 75 (25.3) | 62 (23.7) | 13 (38.2) | |
| Summer | 77 (26.0) | 68 (26.0) | 9 (26.5) | |
| Autumn | 77 (26.0) | 70 (26.7) | 7 (20.6) | |
| Study centre: Basel | 172 (58.1) | 145 (55.3) | 27 (79.4) | 0.007 |
| Maternal atopy ¶ | 91 (30.8) | 85 (32.6) | 6 (17.6) | 0.076 |
| Intrapartum antibiotic prophylaxis | 78 (26.4) | 68 (26.0) | 10 (29.4) | 0.667 |
| Maternal smoking during pregnancy | 12 (4.1) | 10 (3.8) | 2 (5.9) | 0.635 |
| Presence of older siblings | 173 (58.4) | 152 (58.0) | 21 (61.8) | 0.676 |
| Attendance in childcare | 162 (54.7) | 142 (54.2) | 20 (58.8) | 0.610 |
| Maternal infections in third trimester requiring antibiotic treatment | ||||
| Urinary tract/gynaecological infection | 16 (5.4) | 16 (47.1) | ||
| Respiratory infection | 8 (2.7) | 8 (23.5) | ||
| ENT infection+ | 4 (1.4) | 4 (11.8) | ||
| Other infection§ | 2 (0.7) | 2 (5.9) | ||
| Unknown | 4 (1.4) | 4 (11.8) | ||
| Symptoms in first year, weeks | 6.2±5.0 | 6.0±4.8 | 7.2±6.1 | 0.282 |
| Severe symptoms in first year, weeks | 0.7±1.2 | 0.6±1.1 | 1.2±1.7 | 0.030 |
Data are presented as n, n (%) or mean±sd. unless otherwise stated. ENT: ear, nose and throat; #: p-values were obtained using t-test, Mann–Whitney test, Pearson Chi-squared test and Fisher exact test, as appropriate; ¶: defined as bronchial asthma, allergic rhinitis or atopic dermatitis; +: defined as infection of ears, neck, throat, e.g. otitis media; §: defined as infection not classified above, e.g. gastrointestinal infection.