Table 4.

Association between measures of parental fertility and childhood asthma at 7 years in the MoBa

Exposure	Exposure group	N	N cases (%)	Unadjusted RR (95% CI)	Adjusted* RR (95% CI)
Previously treated for unwanted childlessness	No	68 011	2827 (4.2)	1	1
	Yes	6018	325 (5.4)	1.30 (1.16 to 1.46)	1.26 (1.12 to 1.42)
Time to conception	<6 months	60 485	2525 (4.2)	1	1
	6–12 months	9431	386 (4.1)	0.98 (0.88 to 1.09)	0.98 (0.88 to 1.09)
	>12 months	5881	318 (5.4)	1.30 (1.16 to 1.45)	1.19 (1.06 to 1.34)

*Adjusted for maternal age, parity, education, smoking during pregnancy, prepregnancy BMI and maternal current asthma.

BMI, body mass index; MoBa, Norwegian Mother and Child Cohort Study; RR, relative risk.