eTable 3. The effect of combined oral contraceptives on breast cancer risk^*1.

Study	Number		Relative risk	95% CI
	Cases	Controls
Oxford reanalysis, 1996 (19)	53 297	100 239	Current/previous COC: 1.24	1.15–1.33
Nurses’ Health Study, 1997 (cohort study) (e43)	3383		1.11 COC >5 years: 0.96	0.94–1.32
				0.65–1.43
Women’s CARE Study, 2002 (e44)	4575	4682	1.0	0.8–1.1
Women’s Lifestyle and Health Study, 2002 (cohort study) (e45)	103 027		Previous COC: 1.2 C	1.1–1.4
			urrent/previous COC: 1.6	1.2–2.0
Mayo Clinic (metaanalysis), 2006 (e46)	Premenopausal breast cancer		Current/previous COC: 1.19	1.09–1.29
Oxford Family Planning Association Study, 2006 (cohort study) (18)	17 032		1.0	0.8–1.1
Royal College of General Practitioners’ Study. 2007 (cohort study) (17)	46 000 (744 000 woman years)		0.98	0.87–1.1

COC, combined preparations; CI, confidence interval;

^*1data from (20)