Questions and Answers About Pregnancy Tests
Written by: Perry Nichols
Q: How do pregnancy tests work?
A: All pregnancy tests measure the hormone human chorionic gonadotropin (hCG), also known as the "the pregnancy hormone," either in the blood or urine. This hormone is produced by the body after a fertilized egg has implanted itself within the lining of the uterus, and most often occurs six days following conception, although it may take longer in some cases. With every day of the pregnancy, hCG levels increase dramatically.
Q: What are the differences between a blood pregnancy test and a urine pregnancy test?
A: Besides the obvious difference, a urine pregnancy test, often called a home pregnancy test (HPT), is inexpensive, easy to use at home, and generally able to detect pregnancy two weeks after ovulation has occurred. There are two types of blood pregnancy tests used by doctors and both are able to detect the hCG hormone earlier than urine tests, usually six to eight days after ovulating.
The quantitative blood pregnancy test, also called the beta hCG test, measures the precise quantity of hCG in the blood, able to find even the smallest amount, whereas the qualitative pregnancy test is only used to check for the presence of hCG and is roughly as accurate as the urine test.
Q: How accurate are pregnancy tests?
A: Most pregnancy tests boast a 99% accuracy rate, however, that number actually will depend on a few variables, such as whether or not the test was done according to the exact directions, if it was used before the kit's expiration date, or even how long it takes the fertilized egg to be implanted. Some brands may be more sensitive, and every woman's level of hCG will vary, giving accurate results for some sooner than others.
Q: How soon after my first missed period should I take a pregnancy test?
A: Many tests say they can accurately detect pregnancy the first day of your missed period, although research indicates that the majority of home pregnancy tests aren't quite that reliable. One week after the first day of your missed period is the best time to get an accurate reading from most pregnancy tests.
Q: How do you take a pregnancy test at home, and are they expensive?
A: While different brands and types have varying steps, most all home pregnancy tests work in a similar fashion using a small plastic cup, a test stick, or dropper, and some chemicals. One test may involve collecting the urine in the cup for testing, while others require using a test stick placed within the stream of urine.
With all tests, using the first morning's urine is recommended for the most accurate results. The amount of time to complete the test may vary, but is usually only a few minutes before the answer will appear within the test kit's "results window."
Depending on the number of tests within the box or the brand name, most home pregnancy tests are usually between $10 and $20 and are sold over-the-counter.
Q: What may cause a "false positive or false negative" while using a pregnancy test?
A: Most medications will not interfere with pregnancy tests, unless they are some type of fertility drug that contains hCG. False negatives may also occur if the test is done too early in the pregnancy, so it is generally advised to take another test one week after a negative result if you suspect you are pregnant or if the menstrual cycle has not yet started. If negative results still occur, see your doctor for a more accurate blood pregnancy test.
