Normally a fertilized egg implants in the uterus. But if the fertilized egg, implants somewhere other than the uterus, the pregnancy is said to be "ectopic," which means located in an abnormal position.
When an ectopic pregnancy occurs, the fertilized egg usually implants in one of the fallopian tubes. Because the fallopian tube is narrow and its walls are thin, the pregnancy only has to be about the size of a jellybean before the fallopian tube bursts, causing major bleeding.
Occasionally, the fertilized egg may implant on an ovary, in the abdominal cavity, or in the cervix.
Ectopic pregnancies are rare; they occur in about 1 out of every 60 pregnancies. There are certain risk factors that make an ectopic pregnancy more likely.
These risks include: a history of pelvic inflammatory disease, or PID, sexually transmitted diseases such as chlamydia or gonorrhea, a previous ectopic pregnancy, or a previous tubal surgery for infertility.
Treatment of an ectopic pregnancy, either medically or surgically, is necessary to prevent serious, even life-threatening complications.