See ((Ectopic pregnancy))
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The vast majority of ectopic pregnancies implant in the Fallopian tube.
Ectopic pregnancies can grow in the fimbrial end (5%) , the ampullary section (80%), the isthmus (12%), and the cornual and interstitial part of the tube (2%).
Tubal pregnancy at the isthmus or within the uterus, known as interstitial pregnancy, is high as there is increased vascularity that may result in sudden major internal bleeding.
Tubal ectopic pregnancy is caused by a combination of retention of the embryo within the fallopian tube due to impaired embryo-tubal transport and alterations in the tubal environment allowing early implantation to occur.