From Encyclopedia of Sex and Sexuality
A fertilized egg can become implanted in locations other than the uterus. This is called an ectopic pregnancy and it can occur in the fallopian tubes, cervix, ovaries, or the abdominal cavity. Over 95 percent of ectopic pregnancies occur in the fallopian tubes. The incidence of ectopic pregnancy is rising, due to many factors, including sexually transmitted diseases, infertility, and various hormonal medications. In the United States there is one ectopic pregnancy for every eighty births.
Each month, during the mid-portion of the menstrual cycle, the ovary produces an egg. Normally, the egg is picked up by the fallopian tube and the tube relaxes and contracts rhythmically to push the egg toward the uterus. The sperm usually reach the egg while it is still in the fallopian tube. Once the egg is fertilized it will begin to divide into multiple cells and grow in size. This collection of dividing cells continues its course through the fallopian tube and enters the uterus, where it implants. However, if there has been constriction of the fallopian tube due to adhesions, prior surgery, or infection, the fertilized egg can grow too quickly to fit through the tube and finish the journey into the uterus. At other times the tube does not contract well and does not help push the fertilized egg to the uterus. If either problem occurs, the fertilized egg will develop its placenta in the fallopian tube. The placenta will then nourish the embryo, which continues to grow.
In a few days the early pregnancy begins to distend (widen) the tube and can cause pain to the mother. The blood supply to the fallopian tube is not as good as that to the uterus. With the distention of the tube and decreased blood supply the tube can tear, causing bleeding into the abdomen. This blood, in turn, may cause irritation of the abdominal lining that, interestingly, can cause right shoulder pain. If there is a lot of bleeding the woman may feel dizzy or light-headed and eventually may go into shock (severe low blood pressure).
Typically, women experience noticeable changes from a tubal pregnancy (ectopic, in the fallopian tubes), five to seven weeks from their last normal menstrual period. Women may have pain on one side of their abdomen associated with irregular vaginal bleeding or may have no bleeding at all. If any symptoms suggesting an ectopic pregnancy are experienced by a woman who has had sexual intercourse during the preceding two months, regardless of the type of birth control being used, a blood pregnancy test should be obtained as soon as possible. If the test is positive, an ultrasound examination can be helpful in locating where the embryo has implanted. If no pregnancy is seen in the uterus, there are three possibilities: the embryo is normal, in the uterus, but too small be to seen; an ectopic pregnancy exists; or the pregnancy has already miscarried spontaneously. If there is a mass to one side of the uterus and blood in the pelvis, an ectopic pregnancy exists.
When a doctor suspects a tubal pregnancy surgery is usually performed. A long narrow tube, like a telescope, may be inserted through the skin of the abdomen. The doctor can look through this tube, called a laparoscope, to identify the pregnancy in the fallopian tube. Once located, an incision can be made in the fallopian tube and the pregnancy washed out of the tube. From 3 to 5 percent of such women need future therapy to treat a small amount of placental tissue left in the tube.
More definitive surgery may be necessary to remove all or part of the injured fallopian tube. If it is removed, sterility can also result if the other fallopian tube is not working well. This surgery can be done either through an incision in the abdominal wall or through the laparoscope.
A new development in the treatment of ectopic pregnancies is the use of a drug called methotrexate. Treatment with methotrexate results in absorption of an ectopic pregnancy over the next one to three months without surgery. However, rupture of the fallopian tube will occur during treatment with methotrexate, and women who select this therapy must be very closely monitored. The advantage is that there is a high likelihood that the tube will be unobstructed after this therapy. With a single injection of methotrexate, side-effects are rare; however, if repeated doses are used, there can be serious side-effects.
If a woman has an ectopic pregnancy, there is increased risk that the next pregnancy will also be ectopic in the same or opposite tube. Therefore, if someone who has already had one ectopic pregnancy develops symptoms of pregnancy, it is important to make sure the pregnancy is in the uterus. The sooner the site of implantation is located, the sooner an ectopic pregnancy can be treated and rupture of the fallopian tube, with possible hemorrhage and death, prevented.
Unfortunately, the chance of having a future normal pregnancy is reduced to 50–55 percent after one ectopic pregnancy and is further reduced if there have been repeated ectopic pregnancies. If both tubes have been severely damaged, in vitro fertilization (test tube pregnancy) can place the embryo in the uterus to allow its normal development.