Time Trends in Unilateral and Bilateral Oophorectomy in a Geographically Defined American Population

Abstract

Objective: To evaluate trends in the incidence of premenopausal unilateral and bilateral oophorectomy between 1950 and 2018.

Methods: The Rochester Epidemiology Project medical records-linkage system was used to identify all women aged 18-49 years who were residents of Olmsted County, Minnesota, and underwent unilateral or bilateral oophorectomy before spontaneous menopause between January 1, 1950, and December 31, 2018. Population denominators were derived from the U.S. Decennial Censuses for the years 1950-2010, and intercensal year population denominators were linearly interpolated. For 2011-2018, the annual population denominators were obtained from the U.S. Census projections. Where appropriate, overall incidence rates were age-adjusted to the total U.S. female population from the 2010 Census.

Results: There were 5,154 oophorectomies in Olmsted County across the 69-year period between 1950 and 2018, and 2.9% showed malignant disease on pathology. A total of 2,092 (40.6%) women underwent unilateral oophorectomy, and 3,062 (59.4%) women underwent bilateral oophorectomy. More than half (n=1,750, 57.2%) of the bilateral oophorectomies occurred between 1990 and 2009. Until 1975-1979, the incidence of unilateral oophorectomy was mostly higher than bilateral oophorectomy. From 1980-1984 until 2000-2004, the incidence of bilateral oophorectomy more than doubled and the incidence of unilateral oophorectomy declined. After 2005, both procedures declined and converged to a similar incidence in 2015-2018. The decline in premenopausal bilateral oophorectomy over the past 14 years (2005-2018) was most pronounced for women who underwent oophorectomy concurrently with hysterectomy or did not have any ovarian indication.

Conclusion: The incidence rates of unilateral and bilateral oophorectomy have varied greatly across the 69-year period of this study. In the past 14 years, the incidence of premenopausal unilateral and bilateral oophorectomy has decreased. These trends reflect the effects of the initial 2005-2006 publications and the subsequent expanding body of evidence against the practice of oophorectomy for noncancer indications.

Fig. 1.. Flowchart of the study cohort. We included all women undergoing their first unilateral oophorectomy (defined as complete removal of one ovary) or bilateral oophorectomy (defined as second unilateral oophorectomy or complete removal of both ovaries) during the study period. Therefore, some women had more than one procedure during the study period and were counted twice. By contrast, the procedures were counted separately in the flowchart.

Fig. 2.. Incidence per 100,000 person-years of premenopausal unilateral and bilateral oophorectomy in Olmsted County, Minnesota, shown by 5-year age groups from age 18 to 49 years (A) and by 5-year calendar groups from 1950 to 2018 (B). The incidence rates in B were age-adjusted to the total U.S. female population from the 2010 Census.

Fig. 3.. Incidence per 100,000 person-years of premenopausal unilateral or bilateral oophorectomy with (A, C, E) and without (B, D, F) concurrent hysterectomy across three age groups (younger than 40 [A, B], 40–45 [C, D], and 46–49 [E, F] years) and by 5-year calendar groups from 1950 to 2018. Note that the y-axis scale differs for each age group.

Fig. 4.. Incidence per 100,000 person-years by ovarian indication for premenopausal unilateral or bilateral oophorectomy across three age groups (younger than 40 [A‒C], 40–45 [D‒F], and 46–49 [G‒I] years) and by 5-year calendar groups from 1950 to 2018. Note that the y-axis scale differs for each age group. The indication was listed by the gynecologist at the time of the oophorectomy. For women with more than one result, we reported the most severe indication. Cancer indication (A, D, G) includes primary and metastatic ovarian malignancy and risk-reduction surgery for women at high genetic risk of ovarian cancer. Benign ovarian indication (B, E, H) includes suspicion of cancer or benign condition (eg, adnexal mass, endometriosis, cyst), torsion, or other condition (pelvic pain, abscess, oophoritis, ectopic pregnancy). The third group of women did not have any ovarian indication (C, F, I).