| An ectopic pregnancy is a pregnancy that implants and develops outside the endometrial lining of the uterus. 97% of ectopic pregnancies occur in the Fallopian tube. 80% of these occur in the ampulla region of the tube. About 10% occur in the isthmus region and about 5% in the infundibulum region. Only about 3% occur in the interstitial portion of the Fallopian tube. Rarely do ectopic pregnancies occur in the ovary, in the cervix, or in the abdomen. Although these non-tubal and interstitial ectopic pregnancies are rare, they represent nearly 20% of deaths due to ectopic pregnancies. This high danger to life at these locations likely results from massive bleeding when these pregnancies rupture (These abnormal pregnancy locations, unlike the uterus, cannot expand enough to fit the growing embryo; thus these structures can eventually rupture, causing bleeding. The woman can lose enough blood that her life is threatened.)  Click on image for diagram in new window.Most cervical pregnancies occur after a sharp uterine curettage. More than half of the women with a cervical pregnancy need treatment by hysterectomy. Even if hysterectomy is not performed, the prognosis for future fertility is poor. Most abdominal pregnancies occur after the embryo first implants in the Fallopian tube, after which it is expelled from the fimbrial opening of the tube and then implants in the abdomen. An unusual type of abdominal pregnancy may implant in the spleen or liver, which causes massive lethal bleeding in the abdomen. Uncommonly, an ectopic and a uterine (normal) pregnancy may both occur at the same time. This is termed heterotopic pregnancy. Such a circumstance might be more common after drug induced ovulation (such as for in-vitro fertilization) because multiple ovulations can be more likely to occur. Heterotopic pregnancy occurs in 1% to 3% of pregnancies occurring after in-vitro fertilization. The incidence increases with the number of embryos transferred into the uterus. |