Table 3.

Relation of Breast Cancer Risk to Reproductive Surgery Before Menopause in the Women's Contraceptive and Reproductive Experiences Study, 1994–1998

Exposure Variable	No. of Case Patients	No. of Control Participants	Adjusted Odds Ratioa	95% Confidence Interval
Type of reproductive surgery
No reproductive surgery	2,339	2,174	1.00	Referent
Bilateral ovariectomy	349	527	0.59	0.50, 0.69
Partial ovariectomyb without hysterectomy	227	228	0.94	0.77, 1.14
Partial ovariectomyb with hysterectomy	185	224	0.73	0.59, 0.91
Hysterectomy only	490	539	0.83	0.72, 0.96
Tubal sterilization only	900	919	0.96	0.85, 1.08
Duration since bilateral ovariectomy, years
<10	159	179	0.84	0.67, 1.07
10–19	126	218	0.48	0.38, 0.61
≥20	64	130	0.40	0.29, 0.55
Age at bilateral ovariectomy, years
<30	21	58	0.31	0.19, 0.51
30–34	28	56	0.44	0.28, 0.71
35–39	62	120	0.47	0.34, 0.65
40–44	86	144	0.52	0.39, 0.69
≥45	152	149	0.93	0.72, 1.18
Duration since hysterectomy without bilateral ovariectomy, years
<10	183	206	0.86	0.69, 1.06
10–19	256	286	0.80	0.66, 0.96
≥20	236	271	0.77	0.63, 0.94
Duration since partial ovariectomy with or without hysterectomy, years
<10	93	112	0.78	0.59, 1.04
10–19	160	165	0.91	0.72, 1.14
≥20	159	175	0.82	0.65, 1.03

^aAdjusted for age (continuous), race (white or black), study site (Atlanta, Detroit, Los Angeles, Philadelphia, or Seattle), age at menarche (continuous), first-degree family history of breast cancer (yes, no, or unknown/adopted), number of term pregnancies (0, 1, 2, or ≥3), educational status (some high school or less, high school graduate, some college or technical school, or college graduate or higher), and duration of hormone therapy use (never, 0–6 months, >6 months to <5 years, or ≥5 years).

^bNot bilateral; includes women with an unknown number of ovaries removed.