One of the causes of infertility is fallopian tube disease or blocked tubes
Blocked tubes can usually be determined through the hysterosalpingogram (HSG) test. Scar tissue, or adhesions, resulting from endometriosis or abdominal or gynecological surgery (bowel surgery, cesarean section, ruptured appendix, etc.) can block the sperm from travelling up the fallopian tube to meet the egg. Adhesions (scar tissue) can form inside of the pelvis – inside or around the ends of the fallopian tubes and block an egg and sperm from meeting. Adhesions that develop on the ovaries may disrupt ovulation and those that develop inside the uterus (uterine adhesions) may prevent a fertilized egg from implanting properly.
STDs can lead to scarring and cause blocked tubes
Infections, such as Chlamydia or other sexually transmitted diseases can lead to pelvic inflammatory disease (PID). PID can damage the cilia (tiny hairs lining the fallopian tubes) that help to transport the egg. Without normal cilia, the egg may not meet the sperm, or if an egg becomes fertilized, it may not be able to travel to the uterus. This can result in an ectopic pregnancy, which can further damage your tube.
Infection or scar tissue can also cause the affected fallopian tube to fill with fluid and enlarge, a condition called hydrosalpinx. When this occurs, the tube becomes blocked preventing the sperm from travelling up the fallopian tube to meet the egg.
A woman can also have an unusually shaped uterus that prevents successful implantation.