In ectopic pregnancy, ectopic means “out of place,” so an ectopic pregnancy means that a pregnancy occurs somewhere other than in the uterine cavity.
In order for an ectopic pregnancy to take place, a couple of things need to happen differently from the normal process of a pregnancy.
First, following ovulation, the egg must be fertilized and come to rest somewhere other than the endometrium of the uterine cavity.
Next, when it arrives at this destination, it must implant on a surface with a rich enough blood supply to support a developing embryo.
Ectopic pregnancies have been known to occur on various surfaces, including the ovaries, intestines, and most commonly, in the ampulla of the Fallopian tube.
After implantation, the embryo begins developing and growing just like it would in a normal pregnancy.
Over time, a few different things can happen. Sometimes the tissue can no longer provide a sufficient blood supply for the embryo, leading to its death.
On the other hand, if the tissue can supply the embryo with sufficient blood, then hormones from the corpus luteum and placenta can lead to a missed menstrual period and other body changes like nausea and fullness of breasts, which are typically seen in early pregnancy.
If the ectopic pregnancy occurs in the ampulla of the fallopian tube, it eventually runs out of space.
Slowly the ectopic pregnancy stretches the nerve fibers within the wall of the fallopian tube, causing lower abdominal pain.
Eventually, the expansion causes damage to the wall of the ampulla, potentially rupturing the fallopian tube.
A ruptured ectopic can also lead to massive hemorrhaging into the abdominal cavity, and the blood can irritate the peritoneum which can cause referred pain to the shoulder.