A 43-year-old woman presents to the gynecology clinic for routine follow-up after an abnormal Pap smear. She is asymptomatic and denies abnormal vaginal bleeding, discharge, or pelvic pain. A colposcopy and biopsy of the cervix reveal clear cell adenocarcinoma of the cervix. The physician reviews the risk factors for her condition. Clear cell adenocarcinoma of the cervix and vagina is most commonly associated with which of the following risk factors?
