In utero and early life exposures in relation to endometriosis in adolescents and young adults.

OBJECTIVE: Endometriosis is a common gynecologic disorder often associated with severe pelvic pain and infertility with few known modifiable risk factors. We investigated whether in utero and early life exposures are associated with surgically diagnosed endometriosis among adolescents and young adults. STUDY DESIGN: This case-control study, including 295 laparoscopically-confirmed endometriosis cases and 309 population-based controls aged <25 years, was conducted using data from The Women's Health Study: From Adolescence to Adulthood which enrolled participants from 2012 to 2018. Information on in utero and early life factors were collected using a modified WERF EPHect questionnaire at enrollment, including their mother's age at delivery, birthweight, gestation length, exposure to smoking in utero and secondhand smoke during childhood up to age 13, and if the participant was breastfed. RESULTS: Median age at enrollment was 17 years (range 12-24) in cases and 22 years (range 7-24) in controls, with 83 % and 68 % non-Hispanic whites, respectively. The majority of cases (95 %) were rASRM stage I or II at diagnostic surgery. Exposure to breastfeeding in early life was associated with lower odds of endometriosis diagnosis (OR = 0.39, 95 % CI = 0.21-0.74). Exposure to secondhand smoke during childhood due to maternal smoking was associated with increased odds of endometriosis diagnosis (OR = 2.70, 95 % CI = 1.11-6.60). CONCLUSIONS: Among adolescents and young adults, our data suggest exposures to breastfeeding in early life and secondhand smoke during childhood may be associated with endometriosis risk, providing insight into etiologic pathways to be explored in this young population.