Thought "ectopic pregnancy" only refers to pregnancies that develop within the fallopian tubes? Think again! Ectopic pregnancies can take place within every structure of the reproductive system, and even outside of it.
The terms "tubal pregnancy" and "ectopic pregnancy" are mostly used interchangably — even often by medical professionals. They aren't the same by any means, however. While a tubal prenancy is one that develops in a fallopian tube, an ectopic pregnancy can develop in a wide variety of places, ranging from the ovaries to the cervix, and even the bowels! The vast majority of ectopic pregnancies are not viable by definition, and often become life-threatening for the mother if left untreated as well. Interestingly enough, though, some babies do survive an abdominal pregnancy!
Tubal Pregnancy
A tubal pregnancy is one that develops in one of the fallopian tubes. A pregnancy can develop within one of the fallopian tubes because the tube in question is blocked or damaged, by pelvic inflammatory disease, previous surgery, a side effect of tubal ligation or endometriosis, but tubal pregnancies can also strike women with healthy fallopian tubes. Except for ovarian pregnancies and those achieved by IVF, all pregnancies pass the fallopian tubes. It's no surprise that tubal pregnancy is the most common type of ectopic pregnancy, and the most talked-about, by far, then.
Interestingly enough, there are actually different types of tubal prenancy, categorized by the location where the fertilized egg implants itself:
- The egg attaches to the ampullary section of the tube in about 80 percent of all ectopic pregnancy cases.
- The egg attaches to the isthmus, closer to the uterus, in about 12 percent of cases.
- In about five percent of ectopic pregnancy cases, the fertilized egg will implant within the fimbrial end of the tube, which its its very end — so away from the uterus.
- It's rarer for eggs to implant within the cornual and interstitial parts of the tube, and this is seen in about two percent of cases. Because this part is close to the uterus, this type of tubal pregnancy may be missed on an ultrasound scan.
Tubal pregnancies that develop within the cornual and interstitial part or the isthmus are most risky, due to the increased amount of blood vessels in these areas. In the cases of prenancies that develop within the cornual and interstitial parts of the tube, the fetus can also develop further before symptoms become apparent. A rupture can affect not just the tube, but also the uterine wall.
Tubal pregnancies aren't viable. The fetus naturally stops developing in about half of all cases, while surgery or treatment with Methotrexate, which ends and expels the prenancy, is needed in the remaining cases.
Abdominal Pregnancy
How can a fetus develop inside the abdominal cavity, attached to organs such as the intestines? Surprising as it may be, it happens sometimes. Most likely, such pregnancies start off within a fallopian tube and then float into the abdominal cavity, where they can reattach. Abdominal pregnancies may be missed on routine ultrasound scans because they are found in the expected location, often under the uterus. While such prenancies are very risky indeed, there are instances in which babies that developed within the abdominal cavity survived.
The truth about the pregnancy's location may not be discovered until much later on — in the case of Millie-An Pittman from the UK, doctors only found out she was "in the wrong place" after they had already started performing a c-section. Thankfully the baby was fine: though her mom lost 12 pints of blood and needed emergency surgery, Millie-An weighed a very respectable 8lb 7oz.
Rare Types Of Ectopic Pregnancy
Besides the fallopian tubes and the abdominal cavity, ectopic pregnancies can also occur within the ovaries, on the cervix, and even within the scar tissue of a previous cesarean section. Interestingly enough, it's possible to experience a intra-uterine pregnancy at the same time as an ectopic pregnancy as well.
Ovarian Pregnancy
In about 0.2 percent of ectopic pregnancies, an embryo will attach within one of the ovaries — because the egg never left the ovary and ended up being fertilized there. You may be surprised to hear that the common caustive factors of tubal pregnancies, infections and a history of pelvic surgery, don't seem to be responsible for causing ovarian pregnancies, though there is some indication that woman who previously had IVF are at a higher risk. Ovarian pregnancies don't typically develop beyond four weeks. An extremely vascular environment, the ovaries are prone to bleeding, and it's abdominal pain and bleeding that give the problem pregnancy away.
Treatment can involve removing the entire ovary or a part of it — and in the latter case, it may still produce eggs later on. Methotrexate, the "abortion pill", can also be a viable treatment if the ovary hasn't started rupturing yet.
Cervical Pregnancy
Yes, ectopic pregnancies sometimes even implant within the cervix — again, we're talking about approximately 0.02 percent of ectopic prenancies, so it's exceedingly rare, but it can happen. Because the cervix, like the ovaries, is a very vessel-rich environment, this type of pregnancy is especially prone to hemhorrage when medical professionals attempt to remove the attached placenta. Though these pregnancies can be treated with Methotrexate or potassium chloride now, an emergency hysterectomy is unfortunately still a realistic outcome. When rupture occurs, the mother will almost certainly require blood transfusions.
Heterotopic Pregnancy
A heterotopic pregnancy is a complex situation in which a woman is simultaneously experiencing a normal, uterine, prenancy and an ectopic pregnancy. This type of pregnancy is also sometimes referred to as a combined ectopic pregnancy or a multiple-sited pregnancy. Women on ovulation-stimulating drugs are at a higher risk of experiencing a heterotopic pregnancy.
If such pregnancies are diagnosed in a timely manner, the ectopic pregnancy can be treated while the baby developing inside the uterus survives. This is successfully achieved in about 30 percent of all heterotopic pregnancy cases.
Uterine-Scar Pregnancy
Finally, an embryo can implant within the scar of a previous cesarean section. Though technically part of the uterus, this tissue isn't strong enough to support a growing fetus, and will lead to uterine rupture if it isn't detected. The possibility of a pregnancy developing within the scar of a previous c-section is one reason why women who previously delivered surgically require a higher level of care. As in the case of other types of ectopic pregnancy, surgery or Methotrexate are treatment options.
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