A pregnancy test may let you know if you are pregnant. Here are answers to some of the most common questions about pregnancy tests.
How does a pregnancy test work?
Pregnancy tests are designed to tell if urine or blood contains a hormone called human chorionic gonadotropin (hCG). This hormone is made right after a fertilized egg attaches to the wall of a woman’s uterus. This usually happens, but not always about 6 days after fertilization. In pregnant women, levels of hCG continue to rise rapidly, doubling every 2 to 3 days.
What types of pregnancy tests are available?
There are two main types of tests can let you know if you’re pregnant: urine tests and blood tests.
- Urine tests can be done at home or in a doctor’s office. Many women first choose a home pregnancy test to take about a week after a missed period. Home pregnancy tests are private and convenient. These products come with instructions. Follow them closely for the most accurate results. After testing, you can confirm results by seeing the doctor, who can perform even more sensitive pregnancy tests.
- Blood tests are done at doctor’s office, but are used less often than urine tests. These tests can detect pregnancy earlier than a home pregnancy test, or about 6 to 8 days after ovulation. But with these tests, it takes longer to get the results than with a home pregnancy test. Two types of blood pregnancy tests are available:
- A qualitative hCG test simply checks to see if hCG is present. It gives a “yes” or “no” answer to the question, “Are you pregnant?” Doctors often order these tests to confirm pregnancy as early as 10 days after a missed period. Some of these tests can detect hCG much earlier.
- A quantitative hCG test (beta hCG) measures the exact amount of hCG in the blood. It can find even very low levels of hCG. Because these pregnancy tests can measure the concentration of hCG, they may be helpful in tracking any problems during pregnancy. They may also (in combination with other tests) be used to rule out a tubal (ectopic) pregnancy or to monitor a woman after a miscarriage when hCG levels fall rapidly.
How accurate are pregnancy tests?
Waiting at least a week after a missed period may give the most accurate result. Results may also be more accurate if the test is done immediately in the morning, when urine is more concentrated. Urine home pregnancy tests are about 99% accurate. Blood tests are even more accurate than this.
How accurate a home pregnancy test is depends upon:
- How closely you follow instructions.
- When you ovulate in your cycle and how soon implantation occurs.
- How soon after pregnancy you take the test.
- The sensitivity of the pregnancy test.
What should I consider when buying a pregnancy test?
- Cost. Home pregnancy tests come in many different types. Most stores sell them over the counter (without a doctor’s prescription). The cost varies depending on the brand and how many tests come in the box.
- Accuracy. Most tests can be taken as soon as you miss your period. Some newer, more expensive tests say they can be used 4 or 5 days before your period. Even so, they claim the best accuracy only after the date of your expected period.
How do I use a home pregnancy test?
All home pregnancy tests come with written instructions. Depending on the brand you buy, the instructions may vary:
- You hold a stick in your urine stream.
- You pee into a cup and dip the stick into it.
- You pee into a cup and then use a dropper to put a few drops of the urine into a special container.
- Different brands tell you to wait different amounts of time, although most are around 2 minutes.
- Depending on the brand of the test, you may see a line or a plus symbol, or the words “pregnant” or “not pregnant.” A line or plus symbol, no matter how faint, means the result is positive.
- Most tests also have a “control indicator” in the result window. This control line or symbol shows whether the test is working properly. If the control line or symbol does not appear, the test is not working properly.
What do the pregnancy test results mean?
It’s important to know what a positive or negative result means.
If you get a positive result, you are pregnant. This is true no matter how faint the line, color, or sign is. If you get a positive result, you may want to call your doctor to talk about what comes next.
In very rare cases, you can have a false-positive result. This means you’re not pregnant but the test says you are. You could have a false-positive result if blood or protein is present in your urine. And certain drugs, such as tranquilizers, anti-convulsants, or hypnotics, may also cause false-positive results.
If you get a negative result, you are likely not pregnant. However, you may still be pregnant if:
- The test is past its expiration date.
- You took the test the wrong way.
- You tested too soon.
- Your urine is too diluted because you drank large amounts of fluids right before the test.
- You are taking certain medications, such as diuretics or antihistamines.
If you get a negative pregnancy test result, try retesting within about a week to double-check. Some home pregnancy tests suggest doing this regardless of your results.
What if you get two different results?
See your doctor. A blood test is a good idea to confirm results.