Using a pregnancy test can be both an exciting and frightening prospect for many women. Some people get pregnant when they don’t expect to, while others try for years without success. A pregnancy test is one of the best ways to determine whether your life is about to change, with the exception of going to see a doctor, of course. Learning about how pregnancy tests work, when you should take them, and the different types of tests available on the market are important if you are a woman of child-bearing age.
What is a Pregnancy Test?
A pregnancy test is a way to determine if a woman is pregnant, based on certain compounds found in the blood or urine. Pregnancy tests are relatively inexpensive and come in different forms and brands; almost all store-bought tests require a potentially pregnant woman to urinate on a stick, which will change its color or appearance based on the chemical composition of that urine.
How Pregnancy Tests Work?
When a woman becomes pregnant, the first step is conception – when the sperm enters the egg to form the fertilized ovum. That fertilized ovum releases a very distinctive chemical compound called human chorionic gonadotropin (hCG). The release of this chemical occurs after the fertilized egg attaches to the wall of the uterus, which will provide the avenue by which nutrients pass through the mother to the fetus. 
Human chorionic gonadotropin can only be detected in the blood or urine after this implantation process occurs, which could be anywhere from 6-12 days after the egg has been fertilized. After that time, when you use a pregnancy test and urinate on the stick, trace amounts of hCG can be detected, leading to the results showing up on the test. Blood tests for pregnancy also rely on this marker, but they can detect even smaller concentrations than urine tests, making them more accurate.
When to Take a Pregnancy Test?
There is a lot of confusion as to when you should take a pregnancy test, but there are some simple rules to follow.
Most women suspect that they might be pregnant when they miss their period, as that happens regularly and can be predicted within 1-2 days of accuracy. Most doctors recommend waiting for at least 1 week after your missed period before spending time, money and stress on a pregnancy test.
That week will also make the test more accurate, as the release of the key compound for determining pregnancy – human chorionic gonadotropin (hCG) – won’t occur until after your fertilized egg binds to the wall of the uterus. That process can take anywhere from 5-12 days, so taking a test before that implantation occurs can give you a false negative or a false positive. 
While most urine tests can be administered at home, blood tests for pregnancy require a visit to the doctor’s office, but this can be done anytime after the first 48 hours, due to the measurement for a different compound, which will be explained below.
If you pay attention to your expected menstruation cycle and your sexual activity, you should be able to determine a safe and appropriate time to take a pregnancy test.
Types of Pregnancy Tests
As mentioned above, the primary types of pregnancy tests examine the chemical composition of urine and blood to determine whether fertilization has occurred and whether the fertilized egg has bonded to the wall of the uterus.
This is by far the most popular form of pregnancy test, as you can perform these tests at home and they are widely available in stores around the world. The cost of most urine pregnancy tests average between $8-$20. The process is quite simple; when you pee onto a stick or into a collecting cup, there are antibodies covered with a chemical that will bond with human chorionic gonadotropin, the hormone released after implantation. That bonding will give a positive result, while a lack of bonding will deliver a negative result. You can wait 10-15 minutes for this result, depending on the brand.
More advanced (and expensive) digital tests will give you the results of the test faster, in as little as 3 minutes. 
If you want to get a pregnancy test immediately following a possible fertilization, or if you want a more accurate result than a urine test, you can get a blood test done at a doctor’s office. However, while you can get this test done soon after fertilization (as little as 48 hours), the results may take 2-3 days to get back. That being said, the results have more than 97% accuracy, versus an approximate 75% accuracy of Home Pregnancy Tests (due to human error).
There are two types of blood tests that you can get at a doctor’s office – quantitative and qualitative tests. A qualitative test measures whether there is any hCG present in the bloodstream. This result is a simple yes or no, and can be a very accurate determinant of a pregnancy. A quantitative test measures the precise levels of hCG in the bloodstream, which can tell a doctor about any possible complications or problems with the development of the embryo. 
How Accurate are Pregnancy Tests?
At-home pregnancy tests are considered very reliable, when administered properly, and claim to detect 99% of pregnancies. However, this depends on when you administer the test; using one too soon after missing a period or after becoming pregnant could give a false result. At doctor’s offices, pregnancy tests are extremely accurate, but there is always the rare chance of a false result. 
Some of the factors that affect the accuracy of pregnancy test results include your timing of peeing and poorly following the instructions.
The first time you urinate in the morning will be the most accurate indicator of a pregnancy. Sleeping will give your body time to build up hCG in the blood and urine, so there is a higher chance of the test detecting it if you are indeed pregnant. 
Following instruction is also key, because the tests can be complicated, and you have to perform things in a certain order, timed out properly. This is also a very stressful event for some women, which can cause additional forms of human error. Using a pregnancy test that is expired can also lead to false positives or false negatives.
Pregnancy Test Results
If you get a positive result on a home pregnancy test, it means that you are very likely present. False positives do occur, so you will likely want to visit a doctor or a clinic, whether or not you choose to keep the baby. That will give you a chance to discuss your options and next steps. 
If you get a negative result on a home pregnancy test, there is a good chance you aren’t pregnant, but false negatives can also happen. If your period still doesn’t arrive, either take another pregnancy test or visit your doctor, who can use a blood test or an in-office urine test for a more accurate result.
Even if one of the formal urine or blood tests shows up negative at the doctor’s office, there is still a small chance that you are pregnant. Request a different test or visit a different doctor if your period remains absent for another week.