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. Ectopic pregnancy can occur in any woman, of any age, who is ovulating and is sexually active with a male partner. The highest likelihood ectopic pregnancy occurs in women aged 35-44 years.
The greatest risk factor for an ectopic pregnancy is a prior history of an ectopic pregnancy.
Any disruption of the normal architecture of the Fallopian tubes can be a risk factor for a tubal pregnancy or ectopic pregnancy in other locations. 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 (pelvic inflammatory disease) is another risk factor for ectopic pregnancy. Pelvic infections are usually caused by sexually-transmitted organisms, such as Chlamydia or N. gonorrhoeae, the bacteria that cause 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.
Because having multiple sexual partners' increases a woman's risk of pelvic infections, multiple sexual partners also are associated with an increased risk of ectopic pregnancy.
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 half 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.
A history of infertility for two or more years also is associated with an increased risk of ectopic pregnancy.