How does a pregnancy test work?
A pregnancy test detects hCG (human chorionic gonadotropin), a hormone that is secreted by the placenta of a pregnant woman. hCG enters the urine, and this is what the test reads to determine whether you’re pregnant or not.
How Pregnancy Tests Work:
- The urine travels up the absorbent end of the test strip, starting at an area called the result window.
- When hCG is present in your urine, it will bind with anti-hCG antibodies on particles in the test strip. This causes these particles to float closer to the surface, where they can be read when you look at your results.
- When enough hCG has been detected, a positive result line will appear in your results window. No line means you need to try again later, with fresh urine and a new test strip as soon as possible (within 72 hours).
How accurate are pregnancy tests?
When used appropriately, pregnancy tests are extremely accurate. Pregnancy tests purchased at the drugstore are 99 percent accurate. They’re equally as reliable as a urine pregnancy test from a doctor’s office.
Pregnancy tests look for a hormone called human chorionic gonadotropin in your urine (pee) (HCG). Only when you’re pregnant does your body produce this hormone. When a fertilized egg attaches to the lining of your uterus — when pregnancy begins — HCG is released. If your pregnancy test comes back positive, you’re expecting a child. If they’re negative, you’re not expecting a child.
When you take a pregnancy test after you’ve missed your period, it’s the most accurate.
If you use an expired pregnancy test or if you don’t use it correctly, it will be less accurate. So make sure to check the expiration date on the package and read the instructions carefully before using your pregnancy test.
How soon can I take a pregnancy test?
The most accurate time to test is at the first day of your missed period. However, you can also take a pregnancy test any time of day. It’s best to take it at the same time each day for the most accurate results. For example, if you’re testing on the first day of your missed period, it’s best to do so in the morning before eating or drinking anything, as this is when your urine will be the most concentrated with hCG. However, it’s also fine to take a pregnancy test in the afternoon or evening. If you’re testing before the first day of your missed period and are trying to get pregnant, it’s best to do so in mid-morning after having had 8 hours of sleep because that’s when your urine will be most concentrated with hCG (pregnancy hormone).
If you get a negative result and still haven’t got your period within one week of taking a pregnancy test, try testing again using one more home pregnancy kit (as described above). If this shows another negative result and still no period arrives one week later then make an appointment with your doctor so they can rule out other conditions or confirm a positive diagnosis.
How to read pregnancy test results
Depending on the brand and type of the pregnancy test you’ve used, there may be a slight difference to it. Some tests are digital and have words telling you if it’s positive or negative. Other tests require you to look for a faint line to know that it’s positive.
To properly read the pregnancy test results and understand what they mean, follow these guidelines:
- Positive means pregnant: If a line shows up in either section of your pregnancy test, no matter how faint, you are pregnant.
- Negative means not pregnant: If there is no line at all in either section of your pregnancy test (even if the lines shown are an indicator that the test is working), then you are not pregnant.
- Invalid means retake: If there is no control line or a smeared/broken control line in any section of your pregnancy test after taking it, then something has gone wrong with it and you should try again.
If you see a positive line, you’re pregnant
If you see a faint line, it means the test detected hCG in your urine. This is called a positive result. Any positive result is accurate, even if it’s faint. However, a faint line can sometimes be misleading since evaporation lines are also a light color.
These are both accurate results and equally meaningful: they can tell you that you’re pregnant!
What causes faint positive lines on a pregnancy test?
An evaporation test is a familiar method of determining whether or not you’re pregnant. The urine sample is tested in the lab and the results are usually ready to be released within a week. If there are abnormalities, the results will be explained and you may have to go through more testing (such as amniocentesis) before learning whether or not you’re carrying a child
In our case, we did not read the pregnancy test in time and then diluted our urine for too long before putting it on the test. In addition, both times we performed this test, we got different results which indicated that either the sample was diluted for too long or that it was expired.
Does a lighter pregnancy test mean miscarriage?
Sadly, it is possible that a faint line on your pregnancy test could mean you’ve had a chemical pregnancy. The term chemical pregnancy refers to an early miscarriage that happens so early in the process of pregnancy that it’s simply seen as a very faint positive result on the test kit.
The reason for this is that when you have a chemical pregnancy, the egg and sperm do meet up and start to develop, but the body quickly recognizes that something isn’t quite right and stops further development from taking place.
Because this all happens so quickly, there isn’t enough time for your uterus to get ready for implantation, so even if there was an embryo present earlier on in your cycle, by the time you check with a home test kit or visit your doctor for testing there will be no evidence of anything going wrong left behind.
Although not particularly common (only present in around 25 percent of miscarriages) it doesn’t lessen the impact this kind of outcome can have on those who experience it.
What does a faint line look like?
Now, let’s take a look at the most common lines you may see on your pregnancy test.
- Faint Lines (light Line). The line is very faint and pale. It can appear as either blue or pink. If the line appears after 5 minutes, it is considered a positive result. If it doesn’t appear at all within 3 minutes, you got a negative result.
- Evaporating Line (Evaporation Line). This colorless line is caused by the evaporation of urine on the test strip and does not indicate pregnancy. It will soon disappear from your test strip and window screen, but if it gets darker with time, then it’s an indicator of pregnancy or urine contamination that occurred during testing(it can be caused by any colored detergent). You should repeat the test with a new kit to make sure that you get an accurate result!
How can I avoid getting faint lines on my pregnancy test?
Your best bet for avoiding a faint line is to avoid testing early. However, if you are going to test early and you’re concerned about getting a faint line on your pregnancy test, here are some steps you can take to minimize the chance of seeing one:
- Use a pregnancy test with high sensitivity. The lower the number of mIU (milli-international unit) of hCG a test can detect, the more sensitive it is. For example, tests that can detect 25 mIU/ml or less tend to be very sensitive and thus are more likely to show faint lines at an early stage of pregnancy.
- Avoid drinking lots of fluids before testing. Because HCG is found in urine, it’s possible that drinking too much liquid will dilute the amount of this hormone in your sample. This can make it harder for the pregnancy test to detect it and may result in a fainter than a normal line or even no line at all!
What are the different types of pregnancy tests?
At-home pregnancy tests have come a long way since the days of sneaking into your doctor’s office to get an answer. Now, you can take the test from the comfort of your own home (and even use it before you’ve missed your period).
The test works by detecting hCG in your urine. Human chorionic gonadotropin (hCG) is a hormone produced during pregnancy that appears in your blood within about three to four days after fertilization and in your urine around 10 days after conception. Pregnancy tests work by either testing a sample of your urine or by taking a sample of blood. Most at-home tests are urine tests. The test results are usually accurate, but they’re not 100 percent effective at detecting the hormone.
You can buy over-the-counter (OTC) pregnancy tests at most pharmacies, supermarkets, and other stores that sell health care products. They might also be called home pregnancy tests or early response pregnancy tests. OTCs are usually easy to use and give results within a few minutes.
Blood Test Pregnancy Tests:
Blood pregnancy tests are the most reliable form of pregnancy test available. They can be done at home or in a laboratory. The blood pregnancy test can detect hCG as early as 7-12 days after conception. Blood pregnancy tests are usually more expensive than urine tests. The accuracy of a blood test is usually considered to be 99% accurate, but since they require hCG levels to rise to a higher level before they can detect them, they are not as sensitive as urine tests and may take longer to detect a positive result.
Pregnancy test user errors
According to the American Pregnancy Association, pregnancy tests are typically 97% accurate if you use them correctly—but that other 3% can make a big difference. Here are some of the most common mistakes people make when using a pregnancy test, and how to avoid them.
Mistake: Not following the directions
This is probably pretty obvious, but it’s worth mentioning because it’s one of the most common mistakes people make. Follow the instructions on the box to be sure your results will be accurate.
Mistake: Taking it too early
The best time to take a pregnancy test is after you’ve missed your period, or 14 days after you ovulate (whichever comes first). If you test before then, there’s a chance you could get a false negative, which means that even if you are pregnant, the test won’t be able to detect it yet. This is because your body needs time to produce enough hCG (human chorionic gonadotropin), which is what detection tests look for.
Mistake: Using expired tests
Most home pregnancy tests come with an expiration date on the box and/or on each individual test. It’s important not to use them after this date because testing with expired equipment can give false results.
What to Do If You’re Uncertain
If you are uncertain of a faint line on your pregnancy test, there are several things you can do to be more certain.
- Take the test again in a few days. If you still see a faint line, it may be time to visit the doctor for a blood test. If you only saw one faint line on your first test, it’s possible that you may not see any lines at all on another test if it is not close enough to the day of your missed period.
- Visit your doctor or local gynecologist for a blood or urine pregnancy test. You will receive an immediate result from these tests and they are generally more accurate than home pregnancy tests.
- Take the test in the morning because urine is often most concentrated at this time of day, so there is less chance that any hCG in your system will be diluted by water intake during the day–which can make any positive result harder to read. This is particularly important for those who suspect they might be pregnant but have taken their home pregnancy test too early and been left with an inconclusive result.
- Be sure to carefully follow all instructions when taking a home pregnancy test as failing to do so could lead to false results–including false positives and negatives (especially false negatives). You must take care not to expose urine samples or testing devices to sunlight or bright lights before testing as this can also cause unwanted effects on results–particularly with digital tests