Approximately 20% of female infertility can be attributed to tubal causes. Distal tubal occlusion (affecting the end towards the ovary) is typically associated with hydrosalpinxformation and often caused by Chlamydia trachomatis. Pelvic adhesions may be associated with such an infection. In less severe forms, the fimbriae may be aggluntinated and damaged, but some patency may still be preserved. Midsegment tubal obstruction can be due to tubal ligation procedures as that part of the tube is a common target of sterilization interventions. Proximal tubal occlusion can occur after infection such as a septic abortion. Also, some tubal sterilization procedures such as the Essure procedure target the part of the tube that is near the uterus.