What do I need to know about hCG testing?

There’s lots of options when it comes to pregnancy tests, and it can be confusing.  A good place to start is to understand what exactly they’re testing for.  hCG stands for “human chorionic gonadotropin” and is used widely in pregnancy testing.  hCG is a hormone that is produced when a woman becomes pregnant.  hCG is produced in the placenta approximately 4 days after conception (it can vary depending on the woman and the pregnancy).

With a normal pregnancy, hCG levels will generally rise and double every two days throughout the first trimester, before slowly declining. Even though age and other factors, such as the hCG diet or cancer can impact the levels of hCG, it’s still known as the pregnancy hormone.

How is hCG tested?

hCG can be tested using urine or blood.  All home pregnancy tests use urine.  When you go to the doctor, they will either use a urine test or a blood test.  You’re probably very familiar with peeing on a stick, but people generally know less about blood-based pregnancy tests.  Below we’ll break down some of the key differences:

Urine Pregnancy Tests

Urine pregnancy tests are easy, inexpensive and fast. There are multiple brands to choose from and you can find a urine pregnancy test in almost any type of grocery store or pharmacy. Home pregnancy tests use the same technology as your doctor or OB/GYN would use for a routine pregnancy check.  You pee in a cup, write your name on the cup, and put the sample in a cupboard for testing.  Behind the closed door, there is a technician who is dipping a strip test in the urine to test it, or sometimes they may pipette the sample into a fancier test cassette and test for other things such as proteins, sugars and ketones.  Here’s a great resource for more information on urine tests.

Urine tests are facing increasing criticism, as they are proving to be more susceptible to false negative results.  We won’t get too technical in this post, but generally false negatives occur because of one of these reasons:

  • Urine tests aren’t sensitive enough (higher limit of detection).
  • The urine is too diluted (patient drank too much water).
  • The urine isn’t tested in the morning when hCG levels tend to be the strongest (see above point).
  • Something called beta core fragment which causes false negatives in urine tests.
  • Something called “the hook effect” which occurs when hCG levels become so high, which overwhelms the test and causes a false result.

Blood-Based Pregnancy Tests

If you go to the doctor and get a positive result on a urine pregnancy test, they will generally take a blood sample and send it off for final verification of pregnancy.  I won’t get too far into qualitative vs. quantitative tests in this post, but more to come in the future.  Blood is widely known as the most reliable sample type for confirming pregnancy.

Here’s how it’s worked in the past:

  1. A phlebotomist draws blood into a tube(s).
  2. The blood tubes are taken to a central lab, either onsite or offsite.
  3. The lab staff do what’s called spinning downs the blood (centrifuging).
  4. Spinning down the blood gives you either serum or plasma, depending on the type of tubes they used for the blood.
  5. The serum or plasma is tested for pregnancy.
  6. Results are communicated back to the physicians to share with the patients.

You can see how this process can take more time.  The added expense can be worth it, particularly when a woman is about to have a procedure that would be harmful or fatal to a developing fetus.

Will pregnancy testing ever change?

Baby Hopes wrote a wonderful article breaking down the differences of urine and blood testing.  View it. 

There are new technologies emerging, including ours which allows pregnancy testing at the point of care, without having to send samples off to a lab.  If you’re just learning about pregnancy testing, it’s good to know the different types of testing so you can ask your doctor what’s best for you.