Table 2. Association between BMI and infertility in women aged 20–46 years.

Variables		Fertile matched control (n = 3,944)	Infertile womena (n = 986)		Women with primary infertilitya (n = 643)		Women with secondary infertilitya (n = 313)
		No.	No.	OR (95% CI)b	No.	OR (95% CI)b	No.	OR (95% CI)b
BMI, kg/m2
	< 18.5	164	103	1.35 (1.03–1.77)	67	1.34 (0.97–1.83)	33	1.39 (0.92–2.09)
	18.5–25	1,648	715	Ref	480	Ref	231	Ref
	≥ 25	207	148	2.06 (1.61–2.64)	96	2.26 (1.70–3.01)	49	1.77 (1.22–2.58)

BMI = body mass index, OR = odds ratio, CI = confidence interval.

^aFertile matched control was selected from women aged 20–46 who participated in the National Survey on Fertility and Family Health and Welfare in 2009 & 2012 in the Korea Institute for Health and Social Affairs.

^bOR was calculated using stratified age group, and adjusted for education in conditional logistic regression model.