How to check if you're pregnant with a home pregnancy test? Our text will answer the most important questions you may have. We'll also discuss what to do in a case of a negative pregnancy test and what reasons may cause false-positive or false-negative results.

💡 This article is a part of a bigger series, based on our pregnancy test calculator.

What is a pregnancy test, and how does it work?

Women use pregnancy tests to easily check whether they're pregnant or not. Home pregnancy tests are simple to use and non-invasive, meaning that it doesn't hurt to use them. You also don't need special training to operate them. The most common pregnancy test uses your urine to confirm or rule out the presence of a gestation.

A typical pregnancy test looks like a tiny, white tile with two windows. The smaller window is reserved for drops of urine, and the bigger one displays the test result. Another popular type looks like a thermometer, and you need to pee directly on it to receive the results, which are also displayed in a rectangular window. Two dark lines or a plus indicates that you're pregnant, while one single line or a minus indicates an absence of pregnancy. 🤰

Now that we know what it is, we can learn how it works!

All the at-home pregnancy tests detect human chorionic gonadotropin (hCG) in your urine. hCG is a hormone produced first by the embryo and then by the placenta. The pregnancy test contains antibodies which "attack" the particles of hCG present in the urine of a pregnant woman. These antibodies, bonded with the hCG, form the second dark line in your positive pregnancy test.

Pregnancy tests, positive and negative.

You may ask now — why do we need two lines if only one of them detects pregnancy? The first line is simply a check-up point, confirming that the test is working correctly. If the first line doesn't show up, you need to repeat the test.

Is it possible to be pregnant and get a negative pregnancy test result?

The quick answer would be: yes. If you took the test too early, you might be pregnant even though the test hasn't shown it yet. You should wait a few days and try again for it to give more accurate result. Physicians usually recommend to take the test in the morning after the day of your missed period. 📅

Now we may ask ourselves — how is it possible?

The answer is simple: all the pregnancy tests work by detecting hCG. The hCG is produced by the embryo and then by the placenta. As we can expect, the level of hCG rises along with the age of the pregnancy and reaches its peak values around the 10th week of gestation.

Various tests offer different quality and sensitivity, or the ability to detect a certain hCG level in urine or blood. Tests with the highest sensitivity have extremely low cut-off values, which allows them to prove the presence of even a tiny amount of hCG accompanying the gestation. On the other hand, tests with low sensitivity stay "blind" to low levels of hCG and might easily ignore the existence of early pregnancy — this kind of event is called "the false negative".

What if I get a positive test, and then several days later it’s negative?

There are at least a few explanations for this situation. 📍

Firstly, as we all know, no tests are reliable in full 100%. Some of them may give you false negative or false positive results — it simply means that they may tell you that you're pregnant, even though you're not. That might be the reason why you see a negative result after you initially confirmed your pregnancy with a positive one.

Another possibility is that the pregnancy ended by itself. Unfortunately, most early gestations end up in miscarriage — natural pregnancy loss at this stage is very common. In the past, women wouldn't even know that they were pregnant, but nowadays, we can detect even extremely early pregnancies and learn about their course.

What if there is something wrong with the test?

Although this situation is very unlikely, the pregnancy test may give you either:

  • False-negative results;
  • False-positive results; or
  • No result at all.

If your test comes back negative, but you still have apparent pregnancy symptoms and your missed period hasn't returned yet, you may still be pregnant. Sometimes, early in the pregnancy, the pregnancy hormones' levels are too low to be detected by tests of lower quality. This situation is called the false negative pregnancy test.

Suppose you take a pregnancy test, and it turns out positive, but you get a negative result on the second try. In that case, the first test might not be working correctly. Possible causes include using it after its expiration date.

If only the second line in the window turns dark, or there are no lines visible after the test is done, you need to try again with another test, as this one seems to be broken.

Is it possible to get a false positive pregnancy test result?

Yes, it is possible. As the famous saying goes: medicine doesn't know the word "never". A test that would be 100% accurate all the time simply doesn't exist. If you're still not sure whether you're pregnant or not, consult your OB-GYN or general practitioner. 👩‍⚕️

Can ectopic pregnancy not show up on pregnancy test?

Yes, this kind of complication may result in a false-negative test.

Ectopic pregnancy is a gestation located outside of the uterus. Such a situation is relatively rare and can occur in 1/100 cases. Pregnancy tests can detect hCG levels, the pregnancy hormone produced by both the embryo and the placenta. Due to the unnatural location of the implantation, the gestation is not developing correctly. As a result, the amount of hormones produced is often too low for the test to detect.

Will pregnancy test negative after miscarriage?

Yes, the test should turn negative after a miscarriage. The levels of gestation hormones drop drastically right after the end of the pregnancy, and continue to decrease during the next 4–6 weeks.

If the signs of pregnancy are still visible, and your period is late, you should check your hCG and consult your physician. Persistent high levels of hCG might be a sign of a serious disease like cancer or gestational trophoblastic disease. 📍

Łucja Zaborowska, MD, PhD candidate
Have you been wondering when to take a pregnancy test?

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