Final answer:
An ectopic pregnancy occurs when the embryo implants outside of the uterus, and the most common site is the uterine tube.
Step-by-step explanation:
An ectopic pregnancy occurs when the embryo implants outside of the uterus instead of inside. The most common site for an ectopic pregnancy is the uterine tube, also known as a tubal pregnancy. However, ectopic pregnancies can also occur in the ovaries or abdomen.
Once in the abdominal cavity, an embryo can implant into various well-vascularized structures, including the rectouterine cavity (Douglas' pouch), the mesentery of the intestines, and the greater omentum. These structures provide a blood supply for the developing embryo.