Q. A 26-year-old woman comes to her gynecologist for having difficulty becoming pregnant. She and her husband have been trying to conceive for over a year but without success. She attained menarche at the age of 12 years and her periods have been regular since then. Her past medical history is significant for an incomplete abortion which was treated with dilatation and curettage 4 years ago and an episode of pelvic inflammatory disease treated successfully with antibiotics at the age of 18 years. Her temperature is 37°C (98.6°F), pulse is 86/min, respirations are 14/min, and blood pressure is 120/80 mmHg. BMI is 21 kg/m2. Physical examination is unremarkable. What is the most likely cause for her infertility based on her clinical features?