n	%	n	%	P-value
Gender
Boy	1316	50.0	347	52.5
Girl	1317	50.0	314	47.5	0.25
Caesarean section
No	2321	88.2	546	82.6
Yes	312	11.9	115	17.4	< 0.001
Newborn respiratory diagnosis,
No	2491	94.6	625	94.6
Yes	142	5.4	36	5.5	0.96
Older siblings
0	1478	56.1	343	51.9
≥ 1	1155	43.9	318	48.1	0.05
Breastfeeding
< 4 months	486	18.7	175	27.1
≥ 4 months	2108	81.3	472	73.0	< 0.001
Parental history of allergic disease
No	1846	70.8	441	67.3
Yes	762	29.2	214	32.7	0.08
Maternal smoking during pregnancy and/or in infancy
No	2297	87.3	546	82.7
Yes	335	12.7	114	17.3	0.002
Socio-economic status
Blue-collar worker	413	15.9	138	21.2
White-collar worker	2184	84.1	513	78.8	0.001
Child’s overweight at 16 years
No	1572	87.5	296	67.6
Yes	224	12.5	142	32.4	< 0.001

P-value obtained from t-test.

Obtained from the medical birth registry.

P-value obtained from chi-square test.

Includes hypoxia, asphyxia, respiratory distress syndrome and other respiratory conditions of fetuses and newborns (ICD 9: 768–770).

Doctor diagnosed asthma and/or hayfever in combination with reported allergy to pollen or pets in one or both parents.

The mother smoked at least one cigarette per day at any point of time during pregnancy and/or in infancy.

Defined as isoBMI ≥ 25 kg/m².