Table 5. Reproductive and lifestyle factors versus risk of endometriosis in women with a history of infertility.

		Surgically confirmed endometriosis (Group A)				Imaging-diagnosed endometriosis without surgery (Group B)				Wald test between Group A and Group B
		n	Cochran- Armitage trend test	Odds ratio	95% CI	n	Cochran- Armitage trend test	Odds ratio	95% CI
Age (years)				0.995	0.964–1.03			0.959	0.908–1.01	χ2 = 2.4 P = 0.308
Age at menarche (years)	≤11	22	0.016	0.771	0.435–1.37	10	0.081	0.934	0.386–2.26	χ2 = 3.2 P = 0.786
	12	31		ref.		11		ref.
	13	18		0.751	0.411–1.37	5		0.630	0.215–1.85
	≥14	14		0.614	0.319–1.18	6		0.767	0.276–2.13
Length of menstrual cycle at 18–22 years of age (days)	≤25	12	0.005	1.30	0.680–2.50	6	0.011	1.68	0.667–4.24	χ2 = 18.0 P = 0.006
	26–31	59		ref.		23		ref.
	32–49	10		0.430	0.217–0.851	1		0.106	0.014–0.792
	≥50	4		0.369	0.132–1.04	2		0.427	0.099–1.85
Smoking at 30 years of age	Never	60	0.666	ref.		21	0.299	ref.		χ2 = 0.3 P = 0.850
	Ever	25		1.05	0.645–1.71	11		1.23	0.582–2.60
BMI at 18 years of age	<18.5	5	0.196	0.424	0.167–1.08	4	0.598	1.02	0.340–3.05	χ2 = 4.2 P = 0.384
	≥18.5 and <22.5	56		ref.		19		ref.
	≥22.5	24		1.15	0.692–1.90	9		1.24	0.545–2.82

BMI, body mass index; CI, confidence interval.