Ectopic Pregnancy
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? »
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