An ectopic pregnancy occurs when a fertilized egg implants outside of the uterus or not within the uterine cavity. The word "ectopic" refers to something medically that is in the wrong place or position.
In about 98 percent of ectopic pregnancies, the fertilized egg implants within a woman's fallopian tube, the narrow tube that links the ovaries and uterus. This is also called a tubal pregnancy.
In rare cases, the fertilized egg can implant in a woman's cervix, or in a scar from a previous Caesarean section, according to the Mayo Clinic. Rarely, it can also attach directly to a woman's ovary, or to her cervix, or to an organ in the abdomen, such as the abdominal wall.
During twin pregnancies, it's possible — but rare — for one embryo to implant in the uterus while a second implants at an ectopic location, outside of the uterus.
An ectopic pregnancy can be dangerous because when an embryo implants in a location other than the uterine wall, it's unable to develop normally. Locations other than the uterus don't have enough space or the right tissue for the embryo to grow, according to the March of Dimes.
As the embryo grows, it can cause the organ it attaches to, such as the fallopian tube or an ovary, to rupture. If this occurs, it can lead to severe internal bleeding. In some cases, a pregnant woman might die.
"The uterus is a unique organ that can stretch dramatically with a growing pregnancy," said Dr. Jennifer Kickham, an obstetrician and gynecologist, and the medical director of the outpatient gynecology clinic at Massachusetts General Hospital in Boston. "No other tissue in the body has the ability to grow to accommodate a nine-pound baby or twins," she said.
An ectopic pregnancy can be life threatening to a woman when the embryo implants onto locations outside the uterine cavity. That's because the tissue in these areas can't stretch like the uterus and if the embryo implants into the vascular supply, blood vessels can start bleeding, Kickham said.
Although an ectopic pregnancy can be a life-threatening gynecological emergency, most women who experience one can be treated and can have normal pregnancies in the future, she explained.
In the United States, an ectopic pregnancy can affect 1 to 3 percent of all pregnancies, so it affects a significant number of women and is more common than people realize, Kickham said.
Usually the most common complaints of women with an ectopic pregnancy are vaginal bleeding and/or pain in the abdomen or pelvis, especially on one side of the body, Kickham said. Some women may have shoulder pain or lower back pain. There may also be some dizziness or fainting, because of blood loss. Some women may have no symptoms at all until the fallopian tube ruptures.
It's most common for women to experience the symptoms of an ectopic pregnancy 6 to 10 weeks after a missed menstrual period, Kickham said.
Anything that affects the ability of the egg to travel down the fallopian tube into the uterus — such as prior damage to the fallopian tubes, tubal abnormalities or infections that may block the tube — can increase the risk of having an ectopic pregnancy.
The following women may be at higher risk of having an ectopic pregnancy:
- Women who have had a prior ectopic pregnancy.
- Women who have a history of infertility.
- Women who have had sexually transmitted diseases, such as infections caused by gonorrhea or chlamydia.
- Women who have had pelvic inflammatory disease, an infection that can damage the fallopian tubes, uterus and other parts of the pelvis.
- Women who have had endometriosis, a condition in which cells that normally line the uterus implant and grow elsewhere in the body, such as the ovaries or bladder.
- Women who have had scars inside the pelvis from a burst appendix or past surgeries.
- Women who have become pregnant while using an intrauterine device (IUD) or after having their "tubes tied," which is known as a tubal sterilization.
- Women who smoked cigarettes prior to becoming pregnant.
- Women with a history of multiple sexual partners because this may increase the risk of pelvic infections.
An ectopic pregnancy is likely caused by a combination of prior medical history and lifestyle factors, Kickham said. It is not genetic, she explained.
As described above, anything that affects the functioning of a woman's fallopian tubes, such as prior tubal surgeries or pelvic infections, can increase the risk of an ectopic pregnancy. In addition, factors that can slow movement in the fallopian tube, such as cigarette smoking, can also make a woman more likely to have an ectopic pregnancy.
Diagnosis and tests
To diagnose an ectopic pregnancy, a woman who may be complaining of vaginal bleeding and pelvic pain, may be given a blood test to determine her levels of human chorionic gonadotropin (hCG), a hormone that's only present when a woman is pregnant.
Home pregnancy tests measure hCG levels in the urine, but if an ectopic pregnancy is suspected, doctors will look at the results from a blood test instead to measure the amount of hCG present. In a normal pregnancy, hCG levels will roughly double in a period of 48 to 72 hours, but levels may rise more slowly in an ectopic pregnancy, Kickham said.
Besides measuring levels of hCG, women will also need a test known as a transvaginal ultrasound, in which a wand-like device is inserted into a woman's vagina to examine the reproductive organs, including the uterus, ovaries, cervix and fallopian tubes. Ultrasound uses high-frequency sound waves to create images that can identify whether a pregnancy is located inside the uterus or somewhere else.
Sometimes transvaginal ultrasound can detect that this is not a normal pregnancy and the embryo is growing outside of the uterus, and sometimes ultrasound may not be able to pick up an ectopic pregnancy. But if levels of hCG are between 1,500 and 2,000 mIU/mL, an ectopic pregnancy is suspected even if it's not seen on ultrasound.
Once a diagnosis of an ectopic pregnancy is made, it can be upsetting for a woman to learn that she is not having a normal uterine pregnancy, Kickham said. Some woman may ask, "Is it possible to move the pregnancy to the uterus?" she said, but unfortunately, there is no medical technology available to move the pregnancy to the uterine cavity.
Risks to mother
An ectopic pregnancy can be a gynecological emergency because it may be life threatening to a woman, Kickham said. She said that ectopic pregnancies are the leading cause of maternal death during the first trimester, accounting for 4 to 10 percent of all pregnancy-related deaths.
Although ectopic pregnancies usually happen in the first trimester, they can occur later but these are typically the rarer kinds of ectopic pregnancies, Kickham explained.
A woman who has had a prior ectopic pregnancy has an increased risk for having another ectopic pregnancy, Kickham said. But she also added that a lot of women do go on to have a normal intrauterine pregnancy.
Treatment and medication
For a woman who has minimal symptoms, meaning that there is not a concern that her fallopian tube will rupture, treatment for an ectopic pregnancy typically involves medication, Kickham said. She said that women are given an injection of methotrexate, a drug used in cancer treatment. This medication stops the growth of the embryo, which then allows the body to resorb the tissue. A benefit of this treatment is that it does not affect the fallopian tubes.
Methotrexate is typically given as a one-time injection. A woman needs to have her blood drawn twice, on the fourth and seventh days after receiving the drug, so that doctors can see that her levels of hCG have dropped by 15 percent or more during this time period, Kickham said.
If a woman's hCG levels have not been reduced by at least 15 percent, she will need a second injection of methotrexate to make sure her hCG levels are falling. An ectopic pregnancy ends when hCG levels have dropped to zero.
But not all women are good candidates for medication and some may need to undergo surgery to remove the ectopic pregnancy, Kickham said.
Surgery may involve removing the entire fallopian tube, for example. This operation can be done laparoscopically, which is a form of minimally invasive surgery that requires a smaller incision. For that reason, the surgery can typically be done without a woman needing to stay in the hospital overnight, and she will have a shorter recovery time after the operation.
In some situations, a larger incision in the abdomen may be performed during surgery to remove the ectopic pregnancy. Sometimes the fallopian tube may be removed if its damaged and sometimes it can be surgically repaired.
When a woman has a heterotopic pregnancy, where one twin is growing in the uterus and the other twin is an ectopic pregnancy usually in the fallopian tube, it is too risky to treat the woman with medication. A mother will need surgery to remove the ectopic pregnancy in the fallopian tube, but she will be able to go into labor and give birth to the surviving twin developing in the uterus, Kickham said.
Usually, a woman who has had an ectopic pregnancy is encouraged to wait at least three months before attempting to becoming pregnant again, Kickham said. Since an ectopic pregnancy is a type of early pregnancy loss, a woman should take the time to heal from it, both physically and emotionally.
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