Early-Life Exposures and Odds of Adenomyosis: A Population-Based Case-Control Study.

Background: Adenomyosis can confer life-altering symptoms such as pelvic pain. Yet, the epidemiologic study of this uterine condition lags other gynaecologic conditions. This includes the investigation of intrauterine exposures that could disrupt foetal development and contribute to the presence of adenomyosis in adulthood.

Objective: We investigated nine early-life factors and the odds of adenomyosis using data from a population-based case-control study of enrollees of an integrated healthcare system in Washington State ages 18-59.

Methods: Cases (n = 386) had incident, pathology-confirmed adenomyosis diagnosed between 2001 and 2006. Two control groups were employed: hysterectomy controls (n = 233) and randomly selected age-matched enrollees with an intact uterus ('population controls', n = 323). The primary study activity was a structured in-person interview; participants were also mailed a family history questionnaire that included questions on early-life factors. We conducted logistic regression to estimate adjusted odds ratios (aOR) and 95% confidence intervals (CI) for the associations between early-life factors and adenomyosis.

Results: Comparing cases to population controls, our data suggested an 80% increased odds of adenomyosis with younger maternal age at participant's birth (≤ 19 vs. ages 25-29) (aOR 1.81, 95% CI 0.94, 3.50) and a 50% increased odds of adenomyosis for participants who were the fourth or later live birth (vs. firstborn) (aOR 1.51, 95% CI 0.88, 2.59). Among never-smoking participants, our data suggested a 50% increased odds of adenomyosis with intrauterine exposure to cigarette smoking (aOR 1.50, 95% CI 0.92, 2.46). In analyses using hysterectomy controls, these associations were attenuated.

Conclusions: These data suggested that several intrauterine exposures were associated with increased odds of adenomyosis in adulthood. The intrauterine period may be a susceptible window for subsequent development of adenomyosis and warrants further investigation.