Can Doctors Diagnose an Ectopic Pregnancy Using hCG Levels?

A low or slow-rising hCG level could signal that—but not necessarily.

Pregnant Woman In Consultation with Doctor, Abdominal Exam
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Question:

Can Doctors Diagnose an Ectopic Pregnancy by Examining hCG Levels?

"My doctor says that my hCG level is rising too slowly. I have read that a slow-rising hCG level can be a sign of an ectopic (tubal) pregnancy. Does that mean that my pregnancy is ectopic?" —About.com Reader

Answer:

What is an Ectopic Pregnancy?

An ectopic pregnancy is a pregnancy in which the fertilized egg implants somewhere outside the uterus (the womb).

About 95% of the time, an ectopic pregnancy implants in one of the fallopian tubes, which is why an ectopic pregnancy is often called a tubal pregnancy. But an ectopic pregnancy could also implant on the cervix, an ovary, or elsewhere in a woman's abdomen. 

Sadly, an ectopic pregnancy can't survive. In fact, if it's not treated, a fallopian tube might rupture and the mother could experience blood loss so severe that it could end her life. As a result, ectopic pregnancies must be terminated.  

Does a Low or Slow-Rising hCG Level Indicate an Ectopic Pregnancy?

When you're pregnant, your body releases a hormone called human chorionic gonadotropin (hCG). A low or slow-rising hCG level can be a sign of an ectopic pregnancy, but looking at an hCG level alone isn't usually enough for a doctor to diagnose an ectopic pregnancy. Remember that although a slow-rising or low hCG level is a warning sign of ectopic pregnancy, it doesn't mean that you definitely have an ectopic pregnancy.

 

Here are some other possible explanations:

  • You're not very far along in your pregnancy. If tests show that you have had simply one low hCG level, another explanation could be that you are still very early along in the pregnancy. It is much easier to predict whether your pregnancy is ectopic or not after you have had at least two hCG measurements over the span of at least two or three days, because then you can compare the numbers. You can see whether the level is rising, and if so, how quickly it's increasing. 
  • You're further along in your pregnancy. If you do have at least two hCG levels to examine, but the hormone isn't doubling every two to three days, remember that hCG tends to rise more slowly toward the middle and end of the first trimester. So if you are further along in your pregnancy, those levels may be considered normal and there may be no cause for concern. 
  • You're miscarrying. If you're experiencing any vaginal bleeding or abdominal cramping, or if you notice the loss of any pregnancy symptoms (such as breast tenderness, fatigue, and morning sickness), then it's possible that you are having a miscarriage rather than an ectopic pregnancy. When you miscarry, your hCG level stops rising and starts dropping.

What If A Doctor Suspects an Ectopic Pregnancy?

If your doctor suspects that you may have an ectopic pregnancy, he or she may perform an ultrasound (also known as a sonogram), an imaging test that uses high-frequency sound waves, to get more information. If no gestational sac appears inside the uterus by around week five of gestation, that is a red flag that may signal an ectopic pregnancy.

 The physician may also do a pelvic exam to feel for a mass in the fallopian tube and to see if you're experiencing any pain or tenderness. 

If you do have an ectopic pregnancy, your doctor can usually terminate the pregnancy using an injectable drug or minimally invasive surgery. Fortunately, most women who experience ectopic pregnancies go on to have a viable pregnancies afterward.

Source:

Ectopic and Molar Pregnancy. March of Dimes. Accessed: May 24, 2009. http://www.marchofdimes.com/professionals/14332_1189.asp

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