Table 1

Cohort characteristics

SectionVariableCategoryN%
Maternal perinatalLivebirths7206100
Maternal asthmaYes6178.6
No658991.4
Missing00
Maternal atopyYes130518.1
No590191.9
Missing00
Maternal age at delivery<20 years2643.7
20–35 years552176.6
>35 years140619.5
Missing150.2
Mode of deliveryVaginal491668.2
C-section229031.8
Missing00
Hypertensive disorders of pregnancyYes4466.2
No676093.8
Missing00
Gestational diabetesYes4716.5
No669993.0
Missing360.5
Antibiotic use during pregnancyYes225931.4
No494768.7
Missing00
Smoking during pregnancyYes122317.0
No595382.6
Missing300.4
Socioeconomic deprivation—materialQ1-3369651.3
Q4-5322144.7
Missing2894.0
Socioeconomic deprivation—socialQ1-3363350.4
Q4-5328445.6
Missing2894.0
Child perinatalSingletons694796.4
Multiple births2593.6
SexMale463964.4
Female256635.6
Missing10.0
Birth weightLow (<2500 g)7149.9
Adequate (>2500 g)648690.0
Missing60.1
Gestational age at birthTerm (≥37 weeks)627687.1
Pre-term (<37 weeks)92912.9
Missing10.0
Birth weight percentilesSGA76810.7
AGA576780.0
LGA6709.3
Missing10.0
Season at birthSpring (Mar–Apr)177524.6
Summer (Jun–Aug)181725.2
Fall (Sep–Nov)182025.3
Winter (Dec–Feb)179424.9
Missing00
Early lifeNeonatal jaundice requiring phototherapyYes4516.3
No675593.7
Missing00
Bronchopulmonary dysplasiaYes841.2
No712298.8
Missing00
Hospitalisation for lower respiratory illnessYes4816.7
No672593.3
Missing00
Antibiotics use prior to asthma diagnosisYes572379.4
Antibiotics during respiratory illness*424259.9
No148320.6
Missing00
Child atopyYes383453.2
No337246.8
Missing00
Age at diagnosis, yearsMean (95% CI)2.6 (2.6, 2.6)
Missing00
Season at diagnosisSpring (Mar–Apr)160222.2
Summer (Jun–Aug)195627.1
Fall (Sep–Nov)181225.2
Winter (Dec–Feb)183625.5
Missing00
Asthma controlCategoriesControlled372851.7
Partly controlled262936.5
Uncontrolled84911.8
Missing00
  • *Antibiotics dispensed within 2 weeks of a healthcare encounters associated with respiratory morbidity.