Pregnancy Tests An Overview
How Do They Work:
A pregnant woman produces a special hormone that is apparent in her blood and urine. Pregnancy tests look for this hormone which is called human chorionic gonadotropin (hCG), is commonly referred to as the Apregnancy hormone@.
When a fertilized egg is deposited in a woman=s uterus, this pregnancy hormone is produced. The hormone can be detected in a woman=s system approximately six days after conception despite the fact that implantation may not occur until days later. The level of the pregnancy hormone increases daily. Women should be cautious of claims made by over the counter pregnancy tests that they can detect pregnancy on the day that she misses her period. It is recommended that a woman wait at least a week before using one of these tests to ensure accuracy.
Urine Tests vs. Blood Tests
Both urine and blood tests test for the presence of hCG in a woman=s system. A urine test can be purchased over the counter and can be used in the privacy of one=s home. Only a doctor can perform a blood test. A home pregnancy test (AHPT@) is the most common way a woman tests for pregnancy and these tests can detect pregnancy approximately two weeks after ovulation.
If a woman receives a positive result from a HPT, she should consult her doctor in order for him to perform a more accurate blood test. Early medical intervention is essential for a healthy pregnancy.
Doctors can perform two different types of blood tests and both can depict pregnancy 6 to 8 days after ovulation. The first one is a qualitative hCG test which is about as accurate as a urine test and simply gives a Ayes@ or Ano@ answer to the question as to whether a woman is pregnant or not. A qualitative hCG test, a/k/a beta blood test measures the exact amount of hCG in a woman=s test and is, therefore, very accurate.
Home Pregnancy Tests (HPT)
There are many different types of HPTs on the market. They range in price from $8.00 to $20.00, depending on the brand name and the number of test strips in a package.
No matter which type a woman uses, the instructions are similar. Some instruct the user to place the test strip in the urine stream while others instruct the user to dip the test strip into a collection of urine. Every test comes with detailed written instructions which should be followed closely and most tests advise using the test the first thing in the morning to insure accuracy.
Once the test is performed, the waiting game begins. The wait times vary depending on the brand of test used. Once the wait time has elapsed, the results of the test may be viewed in the Aresults@ window. A positive result may be indicated by either a Aplus@ sign or a line. No matter how faint the positive indicator is, a woman can assume that she is pregnant.
Most tests also include a control indicator in the results window to indicate if the test is working properly. If this indicator is not present, the results can be considered inaccurate and another test should be purchased and performed.
Repeating the test in a couple of days is highly recommended no matter what the result. If the user has any questions regarding the use or accuracy of the test, it is recommended that she contact the company via the phone number included in the package.
Accuracy of HPTs
The accuracy of a HPT depends on various factors, including:
- How they are used. The instructions must be followed exactly.
- When they are used: The levels of hCG increases over time. Waiting a week after a missed period makes it easier for the test to depict the presence of this hormone. In addition, as mentioned above, using the first urine of the morning helps the test detect the presence of this hormone.
- Who uses the test. As we all know, women’s body=s are different. Some women may receive an accurate result on the first day that she misses her period. Others will have to wait a while longer before getting an accurate result.
- Brand of the test: Like men, some tests are more sensitive than others.
Researchers tested the accuracy of HPTs in 2004. The only brand to accurately detect the low levels of hCG present on the fist day of a missed period was First Response Early Result Pregnancy Test. Most other tests missed up to 85% of the pregnancies at this early stage but accurately detected pregnancy one week later.
Most Accurate HPT
Some tests are better at picking up low levels of hCG. However, extensive research has yet to be conducted as to which tests do so. Two studies have indicated that the aforementioned First Response Early Result Pregnancy Test may be better at detecting low levels of hCG and therefore, this test is recommended.
How Soon Can a HPT be Performed for an Accurate Result
Despite the claims by test manufacturers that pregnancy can be detected by a HPT on the first day a woman misses her period, research has proven otherwise. Often, tests that are performed too early give convoluted results. It is therefore suggest that a woman wait one week after a missed period before using a HPT.
Accuracy of HPTS depends on the various factors outlined above.
Negative Results and Pregnancy
If a woman obtains a negative result with her HPT, she should take the test again a few days later, just to make sure.
Ovulation occurs at different times, depending on the woman. And as indicated above, implantation of the fertilized egg varies from woman to woman.
False results can be a result of taking the test too early. In some cases, a low level of hCG can be indicative of a problem with the pregnancy.
Factors Effecting HPT results
Any medication that a woman is taking, such as antibiotics, birth control pills, over the counters medicines and prescriptions can interfere with the accuracy of a HPT. Some medicines, such as fertility drugs, contain hCG in them and this, of course, can influence the accuracy of a HPT.
There are many resources for on pregnancy tests such as the National Woman’s Health Information Center at 1-800-994-9662 and the following organizations:
Food and Drug Administration
Phone Number(s): (888) 463-6332
Internet Address: http://www.fda.gov
American College of Obstetricians and Gynecologists
Phone Number(s): (800) 762-2264 for publication requests only
Internet Address: http://www.acog.org/
Planned Parenthood Federation of America
Phone Number(s): (800) 230-7526
Internet Address: http://www.plannedparenthood.org
American College of Nurse-Midwives
Phone Number(s): (888) 643-9433
Related:
Early Pregnancy Symptoms
Pregnancy Symptoms |
