Blocked or damaged fallopian tubes
BMJ Group Medical Reference
About 15 percent of women who haven't been able to get pregnant have damaged or blocked fallopian tubes.  These are the tubes that connect your ovaries to your womb.
Eggs are released from the ovaries and travel down the fallopian tubes towards the womb. If your tubes are damaged or blocked, eggs won't be able to reach the womb.
The most common reason why tubes get damaged or blocked is a condition called pelvic inflammatory disease (PID). This is an infection that can affect the womb, ovaries or tubes. It's very common. This infection can block or damage the fallopian tubes, so that eggs may not be able to pass down the tubes and the sperm may not be able to travel up them.
See Pelvic inflammatory disease to find out more about this condition.
Sometimes the damaged tubes swell and fill with fluid. The fluid can drain into the womb. Doctors think that if a woman with damaged tubes has in vitro fertilisation (IVF) to help her get pregnant, this fluid can make it difficult for the fertilised egg to grow into the lining of the womb. So it may help to have the damaged tubes taken out before having IVF.
See Surgery for women with blocked or damaged tubes to read more.
For references related to Fertility problems click here