Table 1.

Characteristics of the study population (n = 695 infants)

Characteristic			Summary statistic
Anthropometrics
Boys, n(%)			356 (51%)
Gestational age <36 weeks, n(%)			20 (3%)
C-section, n(%)			150 (22%)
Mother asthmatic, n(%)			181 (26%)
Mother antibiotic in third trimester, n(%)			31 (4%)
Siblings, n(%)			392 (56%)
Season of birth
Spring, n(%)			184 (26%)
Summer, n(%)			149 (21%)
Fall, n(%)			148 (21%)
Winter, n(%)			2 (31%)
Clinical information	1 week	1 month	3 months
Samples, n	544	621	623
Antibiotic used, n(%)	11 (2%)	23 (4%)	34 (5%)
Only breastfed, n(%)	477 (88%)	473 (76%)	394 (63%)