What Causes Ectopic Pregnancy–and How Do You Know If it's Happening to You?
In a normal pregnancy, an egg is fertilized in the fallopian tubes and travels to the uterus, where it grows and develops over the next several months. But in an ectopic pregnancy (also sometimes called a tubal pregnancy), the fertilized egg either stays in the fallopian tubes or travels somewhere other than the uterus. This means the pregnancy is not viable—and because it can cause serious complications, surgery or medication is required to terminate it.
About 2% of all pregnancies are ectopic, which means "out of place." Some women are more likely to develop them than others, but the condition can also happen randomly, to women with no risk factors at all. Here's what all women of childbearing age should know about the symptoms, causes, and implications of ectopic pregnancies.
Ectopic pregnancy causes
About 50% of all ectopic pregnancies happen for unknown reasons. “Many times, we have no idea why they take place; the patient has no risk factors and there’s nothing she could have done differently,” says Jenny Jaque, MD, assistant professor of clinical obstetrics and gynecology at the Keck School of Medicine of USC.
The other half of the time, doctors can point to specific factors that may have contributed to the likelihood of an ectopic pregnancy. If a woman has had pelvic surgery or a history of sexually transmitted infection (STI), for example, she could be at higher risk of having an ectopic pregnancy.
“These things can lead to inflammation and scar tissue in or around the reproductive organs, which means there’s a chance for distorted anatomy,” Dr. Jaque says. “That scar tissue can physically get in the way and make it harder for the egg to travel down the fallopian tube and into the uterus.”
Ectopic pregnancies can also be caused by a birth defect that affects the shape and function of a woman’s fallopian tubes or can occur if a woman gets pregnant after having a tubal ligation surgery, also known as having her “tubes tied.”
Ectopic pregnancy symptoms
The first sign of an ectopic pregnancy is often sharp and persistent lower abdominal pain. If a woman has tested positive for pregnancy and begins experiencing this type of pain, it’s important that she get to the doctor right away, says Dr. Jaque.
“The uterus is meant to stretch to accommodate a growing embryo, but your other organs, like your fallopian tubes, are not,” she says. “If an egg implants in the wrong place and starts growing, it could damage or even rupture those organs, which can cause severe pain and bleeding and send you to the emergency room.”
It’s normal for a woman to stop getting her period when she gets pregnant, and that’s true of a normal pregnancy or an ectopic one. But women with ectopic pregnancies may also experience some spotting, or light bleeding. If an organ becomes damaged or ruptures as a result of the ectopic pregnancy, it may cause heavy blood loss and related symptoms, such as dizziness, fatigue, and shortness of breath.
Sometimes, an early ectopic pregnancy can be diagnosed at a prenatal doctor’s visit, before any obvious symptoms occur. “If a woman has a positive pregnancy test and her hormone levels aren’t where they should be, or what we’re seeing on the ultrasound doesn’t match up, then we start suspecting that it may be an ectopic pregnancy,” Dr. Jaque says. Additional imaging tests–typically ultrasounds of the fallopian tubes and elsewhere–are used to confirm an ectopic pregnancy diagnosis.
Ectopic pregnancy risk factors
Research suggests that a woman’s risk of having an ectopic pregnancy may have to do with her age: In one 2014 Iranian study, the risk of ectopic pregnancy for women ages 27 to 32 was 3.9 times higher than for women ages 26 and younger. That number rose to 4.3 times higher for women 33 to 38, and 9 times higher for women 39 and up.
It’s unclear why older women have a higher risk of ectopic pregnancy, the study authors wrote in their paper, but some experts believe they may simply be more likely to have scar tissue in their fallopian tubes, a history of STIs, or age-related changes in tubal function.
Women who have pelvic inflammatory disease—often the result of an untreated STI, such as gonorrhea or chlamydia—are at higher risk of having an ectopic pregnancy. So are women who have had previous pelvic surgeries. “Even something as seemingly unrelated as an appendectomy could lead to scarring and complications,” Dr. Jaque says.
Some studies have also suggested an association between prior abortions and ectopic pregnancies, but others have found no link between the two.
Endometriosis—a condition in which uterine tissue grows outside the uterus—can also lead to the development of scar tissue in the fallopian tubes and increase a woman’s risk of having an ectopic pregnancy. Ectopic pregnancies can also occur if a woman becomes pregnant while she has an intrauterine device (IUD) implanted, although this complication is extremely rare.
Studies also suggest that women who smoke—or who have partners who smoke—may have a higher risk of ectopic pregnancy. The relationship between smoking and ectopic pregnancy isn’t fully understood, but animal studies have shown that inhalation of cigarette smoke may impair the muscle contractions that facilitate movement through the fallopian tubes.
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Ectopic pregnancy treatments
Very few embryos that implant outside of the uterus are capable of surviving—and if the embryo does continue to grow, it can put the mother’s health and future fertility at risk. That’s why prompt treatment is so important, Dr. Jaque says.
If an ectopic pregnancy is diagnosed early, when the embryo is still very small, a woman can be treated with methotrexate—a medication also used in chemotherapy treatments to destroy fast-growing cells. After the drug is administered via injection, a patient’s hormone levels are monitored over the next few days to ensure that her pregnancy has ended.
Sometimes, laparoscopic surgery (also known as minimally invasive surgery) is required to remove the embryo. If an ectopic pregnancy has damaged or ruptured a woman’s fallopian tubes or other organs, she may need more extensive, emergency surgery.
Women who are treated for an ectopic pregnancy can conceive again and carry a pregnancy to full term, although their risk of another ectopic pregnancy is higher than the general public. It’s important that they talk to their doctors about specific risks that may have contributed to their ectopic pregnancy, Dr. Jaque says, and carefully plan their next attempt.
“You should be on contraception until you’re ready to conceive again,” she says, “and have a plan in place with your gynecologist, so you can make sure you’re getting the proper care and monitoring as soon as you get that positive pregnancy test.”