How early can you test for pregnancy?

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You've decided you're ready to start a family, and you want it to happen right away. Finding out if you're pregnant is an exciting process, but waiting for it to happen can really try a person's patience. Just how soon after having sex can you find out if you're pregnant?

You're pregnant when an egg is fertilized by a sperm cell. However, it's nearly impossible to tell you're pregnant the instant it happens because pregnancy is only detectable when it starts producing the hormone human chorionic gonadotropin (hCG). And this doesn't happen until the fertilized egg attaches to the wall of your uterus. For some women, that could take up to six days, and in others it doesn't happen until after a missed period. In other words, it seems to take an eternity.

After the egg's implanted in your uterine lining, your body starts producing hCG. In early pregnancy, the amount of this hormone doubles every two or three days. The presence of this hormone in your urine is what tells you you're pregnant.

Two types of pregnancy tests can help you determine if you'll soon welcome a new addition to your family:

Urine test: With this method, urine has to come into contact with a special stick. You either urinate directly onto the stick or dip it in a cup of your urine. After a few minutes, an indicator on the stick will register whether you're pregnant. Generally, you can take this test as soon as you've missed your period, though some tests can be taken sooner.

Blood test: There are two kinds of blood tests: qualitative hCG and quantitative hCG, also called a beta hCG test. You can take these within seven to 12 days of conception, which means you can test sooner than a urine test [source: American Pregnancy Association]. However, results take longer to get. With a blood test, your doctor will take a blood sample. The qualitative hCG test detects the presence of the hormone in your blood; the quantitative hCG test measures the precise amount.

To take a pregnancy test, you can see your doctor or you can purchase one to take one at home. A doctor's test will give you an accurate result, but a visit may be expensive. Home pregnancy tests are less expensive, and when taken correctly, can deliver quite accurate results. Additionally, they offer the bonus of taking them in the privacy of your own home.

How accurate are these tests? Read on to find out.

Accuracy of Pregnancy Tests

While a blood test is the most reliable way to find out if you're pregnant, home pregnancy tests can also be very accurate -- if you use them correctly. Follow the instructions to the letter and don't use an expired test.

You may also want to take some of the tests' claims on how quickly they work with a grain of salt. Home pregnancy tests can't always detect low levels of hCG, so if you take a test right away, you may not get an accurate result. Waiting at least until you miss your period allows levels of the hormone to build up enough for the test to detect them, and some women may need to wait until a week after a missed period for best results.

Keep in mind that your body doesn't start producing hCG until the fertilized egg implants itself in the uterine lining. Exact ovulation and implantation dates vary by woman. It's quite possible that you could miss a period and be pregnant, but not yet be producing hCG. In that case, a pregnancy test won't work.

Pregnancy tests may also produce false positives and negatives. False positives are extremely rare, but they can happen in the following situations:

  • You were recently pregnant.
  • You take medicine containing hCG.
  • You have blood or protein in your urine.
  • You have ovarian cysts or an ectopic pregnancy.
  • You're going through menopause

False negatives can be more common, and many false negatives are due to these user errors:

  • The test is past its expiration date.
  • You're taking the test too soon.
  • You didn't follow the instructions. The test needs time to work, but if you give it too much time, you may get the wrong results.
  • Your urine is diluted. Take your test when you get up and your urine is its most concentrated.

If you test yourself and get results you don't think are right, wait a few days and take another test. If the results are mixed or you don't get your period, see your doctor, who can do a blood test or discover other factors that may be contributing to a missed period. Irregular periods may also be partly to blame for erroneous test results.

Read on for more information about pregnancy tests.

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Sources

  • American Pregnancy Association. "Taking a Pregnancy Test." March 2011 (April 18, 2011)http://www.americanpregnancy.org/gettingpregnant/takingapregnancytest.html
  • American Pregnancy Association. "Understanding Pregnancy Tests: Urine & Blood." March 2011. (April 18, 2011)http://www.americanpregnancy.org/gettingpregnant/understandpregnancytests.html
  • Healthwise, WebMD. "Multiple Pregnancy: Twins or More - Exams and Tests." July 16, 2009. (April 18, 2011)http://www.webmd.com/baby/tc/multiple-pregnancy-twins-or-more-exams-and-tests
  • Mayo Clinic. "Home Pregnancy Tests: Can you trust the results?" Oct. 30, 2010 (April 18, 2011)http://www.mayoclinic.com/health/home-pregnancy-tests/PR00100
  • National Women's Health Information Center. "Pregnancy Tests." April 1, 2006. (April 18, 2011)http://www.womenshealth.gov/faq/pregnancy-tests.cfm
  • WebMD. "Pregnancy Tests." Feb. 17, 2010. (April 18, 2011)http://www.webmd.com/baby/guide/pregnancy-tests