Medically reviewed by Dr Sai Sudha A/P Ram Moorthi – MBBS (MAHE), MMED O&G (USM), Obstetrics & Gynaecology (O&G), Pantai Hospital Ampang
False positives can really put a roadblock in your pregnancy journey.
Just when you thought you’re finally on the verge of becoming a mother, the at-home pregnancy test throws you a curveball.
The doctor tells you you’re not pregnant.
Well, it’s okay; just keep trying, right?
But don’t be too quick to disregard the dangers of a false positive. They may point to something serious.
Here are some FAQs about getting false positives for your pregnancy tests and what you need to know if this happens to you.
How Do Pregnancy Tests Work?
All pregnancy tests, whether performed at home or at the clinic works by measuring a specific hormone in a woman’s body called hCG (Human Chorionic Gonadotropin).
This hormone is naturally produced by the placenta when implantation occurs (or when a fertilised egg fuses into the uterine lining).
The various at-home pregnancy tests that are widely available in pharmacies are all urine tests.
Whereas clinics make use of both urine and blood tests.
The way pregnancy tests work is through something called monoclonal antibodies, a lab-manufactured protein.
When urine or blood containing hCG is exposed to the protein (and other components such as dyes and enzymes present in the pregnancy test strip) it changes colour, revealing the pregnancy result.
Some more advanced pregnancy tests use digital technology to display their results.
These may even go so far as being able to tell you how far along your are in your pregnancy—typically in terms of weeks or days.
This takes a lot of the guesswork out of the equation.
When Is the Best Time to Take a Pregnancy Test?
Pregnancy tests can be taken anytime you’ve noticed a missed period.
However, most women who are not actively trying to conceive may choose to do so only after experiencing the tell-tale pregnancy signs.
But some tests can now detect hCG much earlier after a successful conception. Typically 3 to 4 days after your missed period.
Another method is to try testing after your last intercourse (very early).
Or more specifically, the last intercourse you had when your ovulation window was open (after 10 days to 2 weeks).
Contrary to popular belief, you don’t automatically get pregnant after intercourse (within 3 to 5 days).
If you’re lucky, fertilisation (when sperm and egg join) can occur within 12 to 24 hours after you’ve had sex. Assuming you’ve utilised your ovulation window to its full potential.
However, it takes another 6 to 10 days for implantation to occur which is when conception technically starts.
Your body, or more specifically, your placenta, is probably producing enough hCG by this time to start giving results.
However, most experts agree that you should let your hCG levels increase before using a pregnancy test, just to be safe.
The general rule of thumb is to wait two to three weeks after intercourse before testing.
The best time of day is usually morning on an empty stomach.
However, some advise to wait a little bit till mid-morning to allow the hCG to accumulate in your blood.
What Affects the Accuracy of Pregnancy Tests?
Many pregnancy tests in the market nowadays have about 100% accuracy. Advancements in science have made them more sensitive and user-friendly.
However, some studies do show that this accuracy level of at-home pregnancy tests is significantly reduced due to user error.
That is, some people may be using at-home pregnancy tests all wrong.
Each product may come with different instructions as well as different ways of reading the results.
When a user commits an error, that’s when you get the wrong test results.
This doesn’t necessarily result in a false positive every time, but it does cause other false results.
For example, a false negative or no results at all.
Other than the cause being a defective product, medical conditions or other very rare and specific issues, the main culprit is usually user error.
At the end of the day, blood tests are a bit more accurate than at-home or clinic urine tests.
This is because blood tests are able to detect even the smallest drop of hCG in your body and determine for sure if you are truly pregnant or not.
How Common Are False Positives in Pregnancy Results?
False positives are extremely rare in most cases.
With the improvement of pregnancy tests, it’s very unlikely that you should get a false positive in your pregnancy tests at all.
To put things into perspective, false negatives occur about 23% of the time.
Meanwhile, false positives occur about only 0.5% of the time.
That’s less than one percent of the time.
So, the chances of you getting a false positive pregnancy result is extremely low.
How Do I Know If I Have a False Positive?
Generally speaking, at-home tests are merely a preliminary test.
You should always go to the doctor to confirm it. This is when you get the real truth about your pregnancy results.
Only a gynaecologist is able to tell if you have a false positive or not.
Not only that, they can also determine what caused the false positive to begin with and whether you need immediate medical attention.
As mentioned previously, while false positives are rare in at-home pregnancy tests, you could also experience a false negative test (which is much more common).
A false negative pregnancy result is where you definitely are pregnant but the test fails to pick up your pregnancy hormones.
9 times out of 10, false negatives are always a result of user error.
Testing too early, before your hCG levels have the chance to rise, can result in a false negative.
However, many at-home pregnancy tests are now able to detect accurate pregnancy results within 5 to 6 days of a missed period.
Why Do Pregnancy Tests Show False Positives?
There are no shortages of things that can cause a false positive pregnancy test.
The first is reproductive issues.
Chemical pregnancy or an early miscarriage can cause elevated levels of hCG in the blood.
These miscarriages happen so early during conception that you may not even notice them.
Ectopic pregnancy is another one. This is where the fertilised egg implants outside of the uterus.
Menopause can also be to blame for false positive pregnancy results.
Another one could be molar pregnancy, where the egg doesn’t develop into a fetus but turns into a benign tumor.
If this is the cause, then you will need to undergo surgery to remove it.
There is also this medical phenomenon called a ‘phantom pregnancy’ or false pregnancy where you experience all the telltale signs of carrying a baby even though you’re not pregnant.
This can also unfortunately cause a false positive pregnancy result.
A false positive result could also be caused by blood or protein in the urine. Unfortunately, this could be a sign of kidney failure or disease.
Taking certain drugs and medications can also cause a false positive in a pregnancy test.
Some examples include anti-anxiety medications, antihistamines, diuretics, antipsychotics, anticonvulsants, and etc.
Certain supplements like biotin have also been shown to affect the accuracy of pregnancy tests.
You might also want to be wary of evaporation lines.
These are lines on the pregnancy test that can look like a positive result but actually aren’t.
They are a natural result of urine drying on the test strip over a period of time.
That’s why it’s important to read the results within the window of accuracy.
Could False Positives Be A Sign of Something Serious?
Yes, the possibility of a false negative being a warning sign of a disease or disorder is very likely.
If you do not fit any of the causes from the above, then it may likely be something else. That’s why it’s important to consult with a doctor if you realise you have a false negative.
There may be other explanations as to why you have elevated levels of hCG in your blood that is not related to pregnancy, medication, or other issues.
Some serious medical conditions that could result in high levels of hCG in the blood include certain types of cancers: myeloma, stomach, liver, lung, bladder, pancreatic, breast, colon, cervical, and endometrial cancers.
However, it is important to go to a doctor where they will be able to pinpoint exactly what caused the false positive result and whether it is something to worry about.
How Can I Reduce Errors in My Pregnancy Tests?
The first advise that medical professionals always give is to read the instructions. At-home pregnancy tests, while effective, can also fail due to user error.
So make sure you understand how to use the pregnancy test before using it.
While there are no specific recommendations for avoiding false positives, you may want to stop certain supplements and medications before taking a pregnancy test.
You can refer to your healthcare provider for this.
Next, never wait too long to read your results.
Some pregnancy tests have a small window of accuracy. After that, it may produce an evaporation line that some people may falsely interpret as a positive result.
To prevent this entirely, you can opt for a digital pregnancy test instead of a normal one.
Lastly, avoid drinking too much water before taking the test.
This will often lead to a false negative instead of a false positive. However, it’s still something to keep in mind.
Getting Accurate Results Every Time
Accuracy is everything in at-home pregnancy testing.
It’s not just about cost but about safety as well as peace of mind.
False positives may be a sign of something serious that needs to be addressed.
Do not delay going to the gynaecologist even after you’ve tested positive for a pregnancy test.
Confirming your results is key to a smooth pregnancy.
With any luck, your false positive could just be an innocent mistake, reminding you that success is just on the horizon.
And all you need to do is try again.
You’ve got this, mummies!
Disclaimer: The information provided in this article is for informational purposes only and should not be considered as medical advice from Motherhood. For any health-related concerns, it is advisable to consult with a qualified healthcare professional or medical practitioner.
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