Without treatment, PID can cause permanent damage to the female internal reproductive organs. Infection-causing bacteria can silently invade the fallopian tubes, causing normal tissue to turn into scar tissue. Scar tissue blocks or interrupts the normal movement of eggs into the uterus. If the fallopian tubes are totally blocked by scar tissue, an egg will not be fertilized by sperm or move to the uterus to develop into a baby. Totally blocked fallopian tubes cause a woman to be infertile.
Infertility can also occur if the fallopian tubes are partially blocked or even slightly damaged.
About one in five women with PID becomes infertile. If a woman has multiple episodes of PID, her chances of becoming infertile are increased. In addition, a partially blocked or slightly damaged fallopian tube may cause a fertilized egg to get stuck in the tube. This fertilized egg may begin to grow in the tube as if it were in the womb. This is an ectopic pregnancy, which is a pregnancy in the fallopian tube or elsewhere outside the uterus.