Fallopian tube obstruction, also known as fallopian tube occlusion, is a major cause of female infertility. Blocked fallopian tubes are unable to let the ovum and the sperm converge, thus making fertilization impossible. In addition, obstruction may impair the transport of a fertilized egg to the uterus, increasing the risk of ectopic pregnancy when implantation occurs outside the uterine cavity, most commonly within the fallopian tube itself.