Fallopian tubes are female reproductive organs that connect the ovaries and the uterus. Every month during ovulation, which occurs roughly in the middle of a menstrual cycle, the fallopian tubes carry an egg from an ovary to the uterus.
Conception also happens in the fallopian tube. If an egg is fertilized by sperm, it moves through the tube to the uterus for implantation.
If a fallopian tube is blocked, the passage for sperm to get to the eggs, as well as the path back to the uterus for the fertilized egg, is blocked. Common reasons for blocked fallopian tubes include scar tissue, infection, and pelvic adhesions.