Wondering how do pregnancy tests work? Here is everything you need to know about a pregnancy test.
If you have been tracking your cycle while trying to conceive or have missed your period, it might be time to take a pregnancy test. This can be an emotional time and you probably are not experiencing any pregnancy symptoms yet, but the only way to know for sure is to take an at home pregnancy test.
This post breaks down everything you need to know including when to take a pregnancy test, how soon do pregnancy tests work, can a positive pregnancy test be wrong, how to read a pregnancy test and so much more.
This post is all about how do pregnancy tests work.
When to take a pregnancy test
The best time to take an at home pregnancy test is about one week after your missed period or two weeks after unprotected sex. This is usually adequate time for enough of the hormone called human chorionic gonadotropin (hCG) to build up in your urine.
You can usually find out sooner with a blood test in your doctor’s office but unless you are considered a high risk pregnancy or are going through IVF (or something similar), you will most likely take a home pregnancy test first.
How do pregnancy tests work?
Pregnancy tests check your urine or blood for hCG. The most common type of pregnancy test is an over the counter home test which looks at your urine specifically.
HCG is only present when a fertilized egg attaches itself to the inside of your uterus (pregnancy) or outside of your uterus (ectopic pregnancy).
When using an over the counter pregnancy test, you will need to do one of the following depending on the test:
- Collect your urine in a cup and dip the test strip in the cup
- Place the test directly in your urine stream
You will need to wait a certain number of minutes (make sure you read the directions) and once the time is up, you will see one of the following:
- A line
- A plus or minus symbol
- A change in color
- The words “pregnant” or “not pregnant”
Although it is recommended to wait one week after your missed period, some tests advertise that you can take the test a certain number of days before your missed period. This is because it has high sensitivity to hCG so it can hypothetically identify even trace amounts of the hormone.
Which pregnancy test should you buy?
Some of the more popular pregnancy tests include those made by First Response and Clearblue. There are usually store brand pregnancy tests available as well. The tests typically come in packs of one, two or three tests and range from about $7 to $15 depending on the brand and store.
Another option is to buy pregnancy test strips. These are a little more difficult to read but are cheaper and come in bigger packs. You can also get a combination of ovulation tests and pregnancy tests when you are trying to conceive. This is exactly what I used and swear by.
Can a positive pregnancy test be wrong?
At home pregnancy tests allow you to have privacy without anyone knowing about it but there are downsides too. These include false positives and negatives as well as user error.
False positives and negatives happen for a variety of reasons but it’s important that once you receive a positive pregnancy test, you call your doctor to schedule an appointment.
Possible reasons for false positives include:
Chemical Pregnancy
This occurs when a fertilized egg (embryo) is unable to implant or grow very early on. They often go undetected if a pregnancy test is not taken.
Ectopic Pregnancy
This type of pregnancy occurs when an embryo implants itself outside of your uterus instead of inside.
It usually occurs when the embryo gets stuck in the fallopian tube during its journey to the uterus but it can also happen in the cervix, ovary or abdominal cavity.
Ectopic pregnancies are considered medical emergencies and must be treated immediately.
Recent Miscarriage
You may continue to test positive following the loss of a pregnancy because hCG can remain in your blood and urine for up to six weeks after the end of a pregnancy.
With a spontaneous miscarriage, any pregnancy-related tissue that was not eliminated will cause your hCG levels to remain elevated. When this occurs a D&C (dilation and curettage) procedure is often required.
User Error
At home pregnancy tests aren’t foolproof. It’s important to read the directions carefully and check the expiration date before taking the test.
One of the most common mistakes is taking the test too early, which can give you a false negative or false positive result.
It’s also important to hold the test stick in your urine for the exact time noted in the directions. The same goes for how long you wait to read the results.
Evaporation Lines
Some at home pregnancy tests show two lines when hCG is detected and one line when it’s not detected.
One line is usually a bright red and the other is fainter. This fainter line may represent a pregnancy or it may be an evaporation line, which may show up after your urine has been evaporated completely.
The best way to avoid this is to follow the set timing for the test as noted in the directions.
Medications
If you are working with your doctor to get pregnant, certain fertility medicines may include hCG to help your follicles release mature eggs.
Other medications that may cause a false positive pregnancy test include those prescribed for anti anxiety, antipsychotics, anticonvulsants, Parkinson’s disease, diuretics, and antihistamines.
Certain Medical Conditions
It is rare that a medical condition causes a false positive pregnancy test result but it is possible.
The medical conditions include urinary tract infection, kidney disease, ovarian cysts, ovarian cancer, and pituitary problems.
Missed period but negative pregnancy test?
It is possible for you to have a missed period but negative pregnancy test. If this is the case, you might have hCG levels that are too low to be detected on an at home pregnancy test. Wait a few days and then take another test.
If you continue to miss your period but have negative pregnancy test results, I recommend calling your doctor to rule out any possible complications.
How to confirm you are pregnant
If you took an at home pregnancy test and received a positive result – congratulations!
False positives are rare but regardless, it is important you confirm the pregnancy at your doctor’s office. Your doctor will most likely conduct another urine test as well as schedule you for an ultrasound and blood test.
It is important to rule out an ectopic pregnancy or any other problems that may occur early on.
What are common pregnancy symptoms?
During the first trimester, you will not look noticeably pregnant yet but you will probably feel it. Between the surge of pregnancy hormones prepping your body for baby and the nausea, sometimes pregnancy can start off a little frustrating.
But remember the discomforts are temporary and it is usually smoother sailing as you enter the second trimester of pregnancy.
Common pregnancy symptoms include:
- Exhaustion
- Nausea
- Headaches
- Mood swings
- Bloating/Cramping
- Breast soreness
- Frequent urination
- Food aversions
- Heartburn
- Stuffy nose
- Vivid dreams
Related: Everything You Need To Know About First Trimester Growth During Pregnancy
I’m pregnant. Now what?
Seeing those two pink lines changes everything but there are a few things that you should do right away.
- Schedule your first prenatal appointment.
- Start taking a prenatal vitamin.
- Find out how far along you are.
- Practice healthy habits.
- Consider changes to your diet.
- Incorporate exercise into your daily routine.
- Check your insurance benefits.
- Get some rest.
- Decide who you’re going to tell.
- Document the journey.
Check out this post for a full breakdown of what to do after positive pregnancy test.
This post was all about how do pregnancy tests work.