What are the Most Common Causes of Ectopic Pregnancy?

An ectopic pregnancy occurs when a fertilized egg is implanted outside of the uterus, typically in the fallopian tube. In almost all cases of ectopic pregnancy, there is no way for the embryo to survive. This type of pregnancy is very dangerous and can lead to severe blood loss and infertility. In many cases, the cause of the ectopic pregnancy is unknown. Some of the common known causes of ectopic pregnancy include fallopian tube blockage, medical conditions, damage from prior surgeries and certain medications.

One of the major causes of ectopic pregnancy is blockage of the fallopian tube. During a typical pregnancy, the egg travels down the fallopian tube and becomes implanted in the uterus. When the egg is unable to make it to the uterus, it might implant in the fallopian tube, a type of ectopic pregnancy known as a tubal pregnancy.

There are numerous ways a fallopian tube can become blocked or damaged. A prior pelvic infection, such as chlamydia or gonorrhea, could lead to pelvic inflammatory disease. Pelvic inflammatory disease can cause inflammation and scarring in the fallopian tubes, which can increase a woman’s risk of having an ectopic pregnancy. Women who use intrauterine devices also are at a greater risk of pelvic infection and fallopian tube scarring.

Some medical conditions are common causes of ectopic pregnancy. If a woman has endometriosis, a condition during which the uterine lining grows outside of the uterus, she could be at a greater risk. Some birth defects or pelvic growths also could lead to structural problems with the fallopian tubes.

Another one of the common causes of ectopic pregnancy is fallopian tube damage from prior surgeries. If a woman has had a tubal ligation, also referred to as having one’s “tubes tied,” and the surgery was unsuccessful, a subsequent pregnancy could be ectopic. When a woman has a tubal ligation reversed, she is at an even greater risk of having an ectopic pregnancy. Additionally, any surgery on the fallopian tubes can cause scarring that could impede an egg’s movement toward the uterus.

Some medications could increase a woman’s risk of having an ectopic pregnancy. Certain hormonal therapies or fertility drugs can affect fallopian tube functioning. Women who have been exposed to the synthetic estrogen diethylstilbestrol (DES) also could be at a greater risk.

Other risk factors might predispose a woman to having an ectopic pregnancy. Those who smoke or are more than 35 years old have a greater risk. Women who already have had an ectopic pregnancy or who have had numerous induced abortions also are more likely to experience this problem.

There is no way to prevent an ectopic pregnancy, but a woman can try to reduce her risk. A woman should use appropriate protection during intercourse to lower her risk of contracting a sexually transmitted disease. Women also can reduce their risk by not smoking.