Table 1 Description of the study population

Female sex

(51)

 Low

(11)

 Medium

(35)

 High

(54)

Parental allergy

(75)

Maternal smoking during pregnancy

(15)

 First year of life

(24)

 Current^a

(15)

 First year of life

(7)

 Current^a

(6)

 First year of life

(45)

 Current^a

(50)

 First year of life

(82)

 Current^a

(76)

 First year of life

(5)

 Current^a

(2)

Older siblings

(48)

Dutch nationality

(95)

Asthma^b

(11)

Did not move house since birth

(52)