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Ectopic Pregnancy

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Ectopic Pregnancy

Stages of Pregnancy Slideshow

Medical Author: Melissa Conrad Stöppler, MD
Medical Editor: William C. Shiel, Jr., MD, FACP, FACR

What is an ectopic pregnancy?

An ectopic pregnancy is a condition in which a fertilized egg settles and grows in any location other than the inner lining of the uterus. The vast majority of ectopic pregnancies occur in the Fallopian tube (98%), however, they can occur in other locations, such as the ovary, cervix, and abdominal cavity. An ectopic pregnancy occurs in about one in 50 pregnancies.

The major health risk of ectopic pregnancy is rupture leading to internal bleeding. Before the 19th century, the mortality rate (the death rate) from ectopic pregnancies exceeded 50%. By the end of the 19th century, the mortality rate dropped to five percent because of surgical intervention. With current advances in early detection, the mortality rate has improved to less than five in 10,000. The survival rate from ectopic pregnancies is improving even though the incidence of ectopic pregnancies is also increasing. The major reason for a poor outcome is failure to seek early medical attention. Ectopic pregnancy remains the leading cause of pregnancy-related death in the first trimester of pregnancy.

What are the risk factors for ectopic pregnancy?

There are multiple factors that increase a women's likelihood of having an ectopic pregnancy, but it is important to note that ectopic pregnancies can occur in women without any of these risk factors.

The greatest risk factor for an ectopic pregnancy is a prior history of an ectopic pregnancy. The recurrence rate is 15% after the first ectopic pregnancy, and 30% after the second.

Any disruption of the normal architecture of the Fallopian tubes can be a risk factor for ectopic pregnancy. Previous surgery on the Fallopian tubes such as tubal sterilization or reconstructive procedures, can lead to scarring and disruption of the normal anatomy of the tubes and increases the risk of an ectopic pregnancy. Likewise, infection, congenital abnormalities, or tumors of the Fallopian tubes can increase a woman's risk of having an ectopic pregnancy.

Infection in the pelvis is another risk factor for ectopic pregnancy. Pelvic infections are usually caused by sexually-transmitted organisms, such as chlamydia or gonorrhea. However, non-sexually transmitted bacteria can also cause pelvic infection and increase the risk of an ectopic pregnancy. Infection causes an ectopic pregnancy by damaging or obstructing the Fallopian tubes. Normally, the inner lining of the Fallopian tubes is coated with small hair-like projections called cilia. These cilia are important to transport the egg smoothly from the ovary through the Fallopian tube and into the uterus. If these cilia are damaged by infection, egg transport becomes disrupted. The fertilized egg can settle in the Fallopian tube without reaching the uterus, thus becoming an ectopic pregnancy. Likewise, infection-related scarring and partial blockage of the Fallopian tubes can also prevent the egg from reaching the uterus.

Like pelvic infections, conditions such as endometriosis, fibroid tumors, or pelvic scar tissue (pelvic adhesions), can narrow the Fallopian tubes and disrupt egg transportation, thereby increasing the chances of an ectopic pregnancy.

Approximately 50% of pregnancies in women using intrauterine devices (IUDs) will be located outside of the uterus. However, the total number of women becoming pregnant while using IUDs is extremely low. Therefore, the overall number of ectopic pregnancies related to IUDs is very low.

Cigarette smoking around the time of conception has also been associated with an increased risk of ectopic pregnancy. This risk was observed to be dose-dependent, which means that the risk is dependent upon the individual woman's habits and increases with the number of cigarettes smoked.

Next: What are symptoms of an ectopic pregnancy? »