For a study, researchers sought to examine trends in the incidence of premenopausal unilateral and bilateral oophorectomy between 1950 and 2018. The Rochester Epidemiology Project medical records–linkage system was utilized to identify all women between the ages of 18 and 49 who lived in Olmsted County, Minnesota, who had unilateral or bilateral oophorectomy before spontaneous menopause between January 1, 1950, and December 31, 2018. Population denominators were collected from the United States Decennial Censuses from 1950 to 2010, and intercensal year population denominators were linearly interpolated. The yearly population denominators for 2011–2018 were derived from US Census forecasts. Overall incidence rates were age-adjusted to the entire U.S. female population from the 2010 Census, when applicable. 

Between 1950 and 2018, there were 5,154 oophorectomies in Olmsted County, with 2.9% showing malignant illness on histology. A total of 2,092 (40.6%) women had unilateral oophorectomy, while 3,062 (59.4%) had bilateral oophorectomy. Between 1990 and 2009, more than half (n=1,750, 57.2%) of bilateral oophorectomies were performed. Until 1975–1979, unilateral oophorectomy was more common than bilateral oophorectomy. Between 1980–1984 and 2000–2004, the prevalence of bilateral oophorectomy more than quadrupled, whereas the prevalence of unilateral oophorectomy decreased. Both operations fell after 2005 and converged to a comparable prevalence in 2015–2018. The decrease in premenopausal bilateral oophorectomy during the last 14 years (2005–2018) was particularly significant in women who had oophorectomy contemporaneous with hysterectomy or had no ovarian reason.

Over the 69-year research period, the incidence rates of unilateral and bilateral oophorectomy fluctuated substantially. The incidence of premenopausal unilateral and bilateral oophorectomy declined during the last 14 years. The changes reflected the effects of the original publications in 2005–2006 and the following growing body of data opposing the use of oophorectomy for noncancer reasons.