At some point in her life, nearly every woman will take a pregnancy test—regardless of the circumstances—which is why it's worth knowing all that you can about them.
1. Paying more doesn't make much difference...
Pregnancy tests vary in price—cheap tests tend to have the classic "line" on their screens, with the pricier tests telling you explicitly whether you're "pregnant" or "not pregnant." Whilst the actual result comes up in a fancier way, spending more on a pregnancy test makes hardly any difference—if you're getting a positive result, you're pretty much getting a positive result however much you've paid for it. It's only really worth dropping more mnoey if you want to know roughly how far along you are straight away, but your doctor will verify this for you anyway.
2. ...but the time you take the test does.
There's a reason the packet recommends you take the test during a morning pee: pregnancy tests work by measuring levels of hCG (or the "human chorionic gonadotrophin" if you wanna get all science-y about it), which is most concentrated in your urine when you go to the toilet first thing. Of course, you could totally take a test at midnight and still get a correct answer, but if you can stand to wait, you'll want to use your test at the beginning of the day for the clearest possible result.
3. You can't really get a false positive.
Pregnancy tests are typically between 97-99% effective, leaving the remaining 3% as a potential margin for error—but "false positives" usually have an understandable explanation. They can happen if you're on certain kinds of medication, such as tranquilizers, anti-convulsants, or fertility drugs, or in many cases, you've had a "chemical pregnancy," where the sperm technically did fertilize the egg, but the pregnancy sadly did not continue. This is actually super common—it happens in around 50-60% of first pregnancies, but most women don't even realize what's gone on. However, if you know about it and you're freaking out, you should know that a chemical pregnancy does not impact your fertility or ability to carry a baby to term in any way, and just because you've had one, it doesn't mean you're more likely to have another.
4. But negative tests don't always mean that you're not pregnant.
It's not just the time of day that has an impact—the time of the month that you take your test can also affect what shows up on that panel. A negative test result, while usually accurate, can also sneakily pop up when you've taken a test too early for the levels of hGC to show, but you do still have a baby growing inside of you. The NHS recommends taking a test from the first day of your missed period, or if your cycle is irregular, at least 21 days after the last time you had unprotected sex, so if your symptoms continue and the test says no on your first try, it's worthing waiting a few days and trying again.
5. They CANNOT tell you the gender of your baby.
This is one pregnancy test myth that seriously needs to be busted—the amount of hGC in your pee can rise equally whether you're expecting a boy or a girl, and no amount of weeing on a special "gender reveal" stick is going to magically tell you otherwise. Any test that promises to tell you "pink or blue" is, honestly, probably lying to you, so it's best to stop Googling most popular baby name lists and picking out nursery colors until after your 20 week scan.
6. They can expire.
Just like contraceptives, pregnancy tests have a best before date, and once it's passed, the chemical used to detect hGC is no longer effective—meaning that your result could be inconclusive. Whether you're actively trying to conceive and have stocked up on a stash of tests, or you've got one leftover in the cupboard from the last time the condom split, it's important to check the numbers on the box before you use them. If your period still doesn't come, you're being sick in the morning or have any other early sign of pregnancy, and tests are still coming up negative, it's time for a trip to the doctor—either you do have a (secretive) bun in the oven, or something else is going on—and regardless of which one it is, you need to get checked out.
This article originally appeared on Cosmopolitan.co.uk. Minor edits have been made by the Cosmo.ph editors.