Back in your mom's day, you had to miss your period before you took a pregnancy test — and wait a couple of hours before you knew the results. These days you can find out you're expecting much earlier, faster and with better accuracy using home pregnancy tests.
All pregnancy tests measure the same thing: urinary levels of human chorionic gonadotropin (hCG), a placenta-produced hormone of pregnancy.[1] HCG finds its way into your bloodstream and urine almost immediately after an embryo implants in the uterus. However, it does take some time before concentrations are high enough to be detected.
When should you take a pregnancy test?
Your best bet is to wait to take a pregnancy test until about 19 days after fertilization in order for hCG to build up to a level that’s detectable in your urine. HCG production begins as soon as the embryo implants in your uterus, which is between six to 12 days after fertilization.
As soon as a test can detect hCG, it can show you (depending on the brand) an extra pink line, a blue one, a positive sign or a big digital yes — all indicating a positive result.
How soon can you take a pregnancy test?
Can't wait to pee on that stick? Understandably, you're likely wondering how early pregnancy can be detected by a home pregnancy test. Although it'll be hard to wait even a few days to find out whether there's a baby in your future, you may be wasting your money if you try taking a pregnancy test the morning after you hope you conceived.
While home pregnancy tests are growing ever more sensitive and accurate, there is a limit to how soon a pregnancy test you buy can work. If you test just seven days after ovulation, pregnancy tests generally can't pick up the very low levels of hCG in your urine. That means you'll likely get a "false negative" even if sperm has met egg.
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There are, however, some brands of pregnancy tests that claim they’re sensitive enough to detect hCG up to five or six days before your missed period. Still, you’ll get the most accurate results (and avoid the disappointment of a potential false negative) if you can wait until the day your period is expected.
How to take a pregnancy test
The details of how you should use a home pregnancy test vary by brand — but in general, it's probably the simplest test you'll ever take. To improve accuracy:
- Don’t drink too many liquids before you take the pregnancy test. It can dilute hCG levels.
- Check the expiration date, and avoid using an expired pregnancy test.
- Read the package directions thoroughly, and follow them meticulously. You'll either hold the test stick in your stream of urine for a few seconds, or collect your urine in a cup and dip the stick into it.
- Wait — but not for long. Follow the directions for when to read the test and how to identify a positive result. You'll see a control indicator (either a horizontal or vertical line, a filled-in circle or a flashing control symbol in digital tests) to let you know that the pregnancy test is working. The result itself requires a couple minutes. And yes, it’s true that any line you see in the pregnancy test result panel, no matter how faint it is (or no matter how faint you feel), means that there's hCG in your system — and a baby in your future.
How accurate are pregnancy tests?
It depends on when and how you use them, but some pregnancy tests claim to be up to 99 percent accurate if you follow the instructions — although experts say in reality accuracy is closer to 75 percent. A few factors that determine how accurate your home pregnancy test will be:
When you take the pregnancy test
Some tests can give an accurate result days before you miss your period. But if you wait until the day your period is supposed to start — at which point your body is producing enough hCG for the test to more accurately detect it — you have a 90 percent chance of the correct result.
When the embryo implants
In 10 percent of women, implantation doesn't occur until the first day of their missed period, which means they might not get an accurate reading even until they wait until a day or two after they miss their periods.
So with every additional day you wait, there's a better chance you'll have hCG in your system, and the home pregnancy test gets more accurate.
How concentrated your urine is
Pregnancy tests used to recommend using your first pee of the morning, when more hCG is present. But now they're sensitive enough to work at any point in the day, although it does help if you're taking the test early.
Similarly, drinking too much liquid beforehand could dilute your urine and affect the results.
Are there different types of home pregnancy tests?
Though different brands show results differently (some with double pink or blue lines, some with a plus or minus sign, some with words like "yes"/"no" or "pregnant"/"not pregnant"), and they range in price, they all work the same way: by detecting levels of the hCG pregnancy hormone in the urine, which begins to appear shortly after implantation.
How much do pregnancy tests cost?
How much pregnancy tests cost depends on the specific type and brand of home pregnancy test. They usually come in packs of two or three, which cost anywhere from $5 to $25.
Can medications affect pregnancy test results?
Most medications won't affect the accuracy of home pregnancy tests, although fertility drugs containing the hormone hCG are a notable exception.[2] If you're not sure, check the package or talk to your doctor.
Can you get a false positive pregnancy test? What about a false negative pregnancy test?
Yes, you can get both a false positive pregnancy test and a false negative. But false positives are much less common than false negatives. So if your home pregnancy test is positive, it's likely that you're pregnant.[3]
If you get a false negative pregnancy test result, it's likely either because you've taken the test too early or you haven't taken it correctly as outlined on the label.
It is possible to get a false positive result on an early pregnancy test before a subsequent test comes back negative. In some cases, that's because very early testing detected a chemical pregnancy — an egg that was fertilized but for some reason never implanted. These very early miscarriages are actually extremely common, accounting for around 3 in 4 of all pregnancy losses (and because they happen so early, the vast majority of women who’ve had one don’t even know they’ve conceived).
If it turns out that you likely have experienced a very early pregnancy loss, it’s natural to feel confused or upset. Knowing the odds are in your favor to conceive again — and give birth to a healthy baby — can help. No matter what, it’s always best to see your medical practitioner to get a more definitive pregnancy test result.
What should I do if I get a positive pregnancy test?
Your best bet is to visit your health care provider to have your result confirmed by a blood test — which measures hCG levels in your blood and can detect pregnancy with nearly 100 percent accuracy. At the same time, you can ask for a complete prenatal checkup. And if your positive pregnancy test is confirmed by your doctor, congratulations!
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