Uterine disorders Quiz: Ace Your Exams

A 26-year-old nulliparous woman presents to the office for the evaluation of infertility. She has been monogamous with her male partner for two years and has had unprotected intercourse regularly since then. She has also been experiencing episodic dull pelvic pain for the past 3 years that usually begins 3 days before menses and resolves after menstruation. She also complains of pain during sexual intercourse for the past 6 months. Her menstrual cycle is regular with periods occurring every 25th day and lasting for 6 days. She usually soaks 5-6 pads during her periods. The couple is currently not using contraception and has no history of sexually transmitted disease. She has had no hot flashes. Speculum examination reveals a moist vaginal mucosa with no abnormalities. Pelvic examination shows a normal-sized retroverted uterus. There is tenderness and nodularity in the posterior cul-de-sac. Semen analysis of her partner is normal. Which of the following is the most likely cause of infertility in this patient?