How Do Pregnancy Tests Actually Work?

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How Pregnancy Tests Actually Work

Posted by The MAB Team on 4/7/2011 to Products
When it comes time to test for pregnancy, it can be very exciting. It can also be scary. It can be a time filled with anxiety while waiting for those greatly anticipated results! There is so much riding on the question ‘will there be one line or two?!

There is of course all of the preparation you have done leading up to this moment, but there is one step that many don’t spend very much time thinking about. What pregnancy test should I purchase? Which tests are most accurate and reliable, but don’t cost an arm and a leg. There really are so many choices out there these days!  It can be quite overwhelming.

But there are definitely differences between the various alternatives you have to make your decision, and having a little bit of knowledge to back you up can be quite helpful.

Knowing what to buy, and where, is something to think about. Some online companies offer better product than can be found on store shelves, and for a fraction of the price. Ultra sensitive pregnancy tests that can detect pregnancy in as few as 3 days after conceiving are available for an extremely low price in comparison to your local drug stores pricing. Not only that, but with the wide range of shipping options available, your product can be delivered to you directly, the next day!

So, how do the tests work, and what are the differences? First we’ll start with the basics.

If your egg was fertilized by your partners sperm, the fertilized egg will travel into the uterus and implant in the uterine lining. When this occurs, the fertilized egg then starts secreting the pregnancy hormone called human chorionic gonadotropin (HCG).

HCG can be found in your urine as early as 6 days past ovulation. Very sensitive home pregnancy tests can detect your pregnancy in as little as 3 days after conception.

How the Tests Actually Work

The pregnancy tests on the market today are manufactured with monoclonal antibodies that detect minute traces of HCG.

When you take a home pregnancy test, you need to soak a portion of the test in your urine (Dip tests and midstream are the two types of pregnancy tests available for home use). As your urine moves up the test into the testing area, you will see a control line which is always present and, if you are pregnant, another line. This line is caused when the HCG in your urine reacts with the monoclonal antibodies, creating a distinct color change. The color of this line will vary in intensity based on how much HCG is in your urine.

The ultra sensitive tests vary from the normal sensitivity tests by its ability to detect a smaller amount of the HCG hormone than that of a regular sensitivity test.

You will be able to determine the difference in the testing by the mIU measurement listed. In it's simplest terms, the number (e.g. 25 mIU) is just a standardized measurement system that detects the pregnancy hormone in your urine. The lower the number the higher the sensitivity! For instance, a test that reads10 mIU, is a highly sensitive test. A test that reads 25 mIU indicates normal sensitivity to the HCG hormone.  Essentially the higher the sensitivity the earlier you will detect your pregnancy.

Doctor’s Office Pregnancy Tests versus Home Pregnancy Tests:

The urine pregnancy tests performed at most doctor’s offices are basically the same kind as the ones found over the counter, or through online distributors. The main difference in pregnancy testing is that some health-care professionals will use blood pregnancy tests, which can detect a pregnancy much earlier than urine tests can. Another advantage of a quantitative blood test is that it can reveal the exact amount of hCG in the blood. This is helpful to assess how far into a pregnancy a woman may be or if there is the possibility that a woman may be miscarrying.

Tips For Getting Accurate Results

Be sure to read the test instructions carefully, taking special notice of the test reading time. Most home pregnancy tests will tell you not to read your test after a certain amount of time. If a line appears after this time period, it should not be counted as a positive pregnancy test. What you may see is an evaporation line, usually colorless, but slightly darker than the color of the pregnancy test membrane. Evaporation lines can occur as your urine dries on the test.

Using first morning urine is a good way to make sure the HCG in your urine is concentrated, making it easier for the pregnancy test to return a positive result if you are pregnant.

Negative Test Results:

Home pregnancy tests usually state a 99% accuracy rate. There is a slim chance that you could end up with either a false-negative result (meaning that you really are pregnant), or a false-positive reading (the test says that you’re pregnant when you are not).

A false-negative test result can occur if:

  • Your urine is diluted - Many tests suggest that you perform the test in the morning, right after you wake up. This is because your urine is usually the most concentrated at this time.
  • You have timed the test incorrectly - It is important that you perform the pregnancy test within 15 minutes after collecting a urine sample. Make sure that you follow the test’s instructions as to how long it takes to analyze the results.
  • Even if you receive a negative result, if your period has not started within a week after a taking the test, you should take another pregnancy test.

Positive Test Results:

Typically, if you receive a positive result (even if it is very faint), this indicates that you are pregnant.

You may end up with a false-positive if:

  • You are taking a prescription medication that contains hCG, such as Pregnyl, A.P.L., Profasi, Chorex, Novarel, or Ovidrel or the medication promethazine (used as an antihistamine in combination cough and cold products).
  • You have traces of blood or protein in your urine.
  • You are currently taking diuretics.
  • You had what is known as a chemical pregnancy. This means that a fertilized egg did implant into your uterus and developed just enough to trigger the production of HCG, but then, for whatever reason, stopped developing. Typically, about 30 to 50 percent of all fertilized eggs end up as chemical pregnancies. When this occurs, most women will end up getting a period (though it may be a few days later or heavier than usual).
If you receive a positive result on a home pregnancy test, you should make an appointment to see your health-care professional. Your health-care professional may perform a blood test or pelvic exam to confirm your positive pregnancy result. The sooner you know whether or not you are pregnant, the sooner you can start to make decisions about your pregnancy.

Once you get to his stage, congratulations!

All of the hard work has paid off! Now it’s time to concentrate on providing a loving home for the developing fetus which includes proper diet, exercise and a good prenatal vitamin to ensure your body, and baby have all the nutrients they need for development!

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