Table 4. Adjusted odds ratio and 95% confidence interval for endometrial cancer in relation to causes of infertility in the E2C2 pooled analysis.

	Cases (n=7877)		Control (n=11 466)
	N	%	N	%	ORa	95% CI
Sought medical attentionb
Never infertile	5573	72	8957	79	1.00	—
Did not seek attention for infertility issues	778	10	852	7	1.16	(1.02–1.31)
Sought medical attention for infertility issues	1398	18	1565	14	1.24	(1.13–1.37)
Unknown (among women who reported having infertility issues)	128	—	92	—	—	—
Cause investigationb
Never infertile	5573	81	8957	87	1.00	—
Cause identified	953	14	851	8	1.31	(1.17–1.48)
Cause not identified	342	5	441	4	1.22	(1.03–1.44)
Cause not investigated	36	1	43	0	1.11	(0.68–1.82)
Causes found (not mutually exclusive)
Endometriosisc
Never infertile	5573	87	8957	93	1.00	—
No, infertility not due to endometriosis	731	11	546	6	1.28	(1.12–1.47)
Yes, infertility due to endometriosis	136	2	87	1	1.80	(1.34–2.42)
Anovulation/PCOSa
Never infertile	5573	92	8957	95	1.00	—
No, infertility not due to anovulation/PCOS	343	6	277	3	1.07	(0.89–1.29)
Yes, infertility due to anovulation/PCOS	124	2	182	2	1.28	(0.98–1.67)
Structural defectse
Never infertile	5573	87	8957	93	1.00	—
No, infertility not due to structural defects	398	6	299	3	1.15	(0.97–1.37)
Yes, infertility due to structural defects	405	6	330	3	1.35	(1.13–1.62)
Male factorsf
Never infertile	5573	92	8957	96	1.00	—
No, infertility not due to male factors	333	5	255	3	1.14	(0.95–1.38)
Yes, infertility due to male factors	156	3	127	1	1.21	(0.93–1.59)

Abbreviations: CI=confidence interval; OR=odds ratio; PCOS=polycystic ovary syndrome.

^aAdjusted for age, study site, race, ever oral contraceptive use, ever menopausal hormone therapy use, parity, interview year and body mass index. Missing set as separate category for each covariate.

^bBased on 13 studies.

^cBased on 9 studies.

^dBased on 8 studies.

^eBased on 9 studies.

^fBased on 8 studies.