Can Sperm Cause a Positive Pregnancy Test: The Science of how Pregnancy begins

Written by Maria
Last updated:
Reviewed by Margaret

The article has been reviewed by medical expert Margaret Dogwood, BSN, RN

A simple answer to this question is no. A sperm does not cause the positive pregnancy test in any way. However, if you plan to be a mother, you must be attentive to other concerns. Many different factors can contribute to false test results. There are other questions, tips, or do’s and don’ts backed by science for a better understanding. Let’s look at everything you need to know about the pregnancy test.

Can Sperm Cause a Positive Pregnancy Test?

No, Sperm cannot result in a positive outcome of the test. The testing device we use for this purpose detects the presence of a hormone called human chorionic gonadotropin (hCG). If the amount of this hormone is rising in a woman’s body, it means she is pregnant. Why?

The woman does not produce these hormones herself. The placenta produces it for developing a connection with the woman for food and oxygen. It means it happens after the fertilization has taken place. In simpler words, the presence of hCG hormones means the woman is already pregnant. 

Sperm cannot create these hormones. If the sperm is there, it will not affect the positive pregnancy test. You will be fine with this while taking the test, and the positive result will most likely be correct. 

Can I Take a Pregnancy Test Right After Sex?

Are you asking if you can get pregnant right after sex? Then the answer is no. You may not take the test right away for this purpose. The test results are based on the presence of hCG hormones which appears after fertilization. The pregnancy occurs 6-12 days after sex, and you won’t get a positive result from the test.

Are you asking if the recent sex can cause false test results? The answer is still no. As we discussed, sperm do not produce hCG hormones. Their presence will determine the correct results. If you take tests right after sex, it means you won’t have a false positive pregnancy test. 

What Causes False Positive Pregnancy Tests?

Sometimes, you may get positive results in the tests. But those results can be wrong and can bring false hopes. Many factors can cause inaccurate results. Let’s have a look:

Evaporation Line

The testing kit has a time limit in which you can use it. After that period, the device will not give you the results. But how do you know if it is functional? A line appears on the device, which means it is not usable anymore. Many women misunderstand this line for a positive result. So, it is essential to know the difference between these lines.

Chemical Pregnancy

Sometimes the chemical pregnancy can also cause a false positive pregnancy test. It is a phenomenon in which fertilization occurs but does not implant. Since it fertilizes, it will release some hCG hormones, and you may get a positive result. It is also known as early miscarriage. 

Medical Conditions

Many diseases can cause false positive pregnancy tests. Any ovary or testicular conditions that produce hCG hormone affects the rest results, as your testing kit will detect these hormones. Many types of cancer can also give false results. The same goes for all the medications that create these hormones. So, if you have any medical condition, consult with your doctor for a better understanding.

Residual Hormone

We know the presence of hCG hormones is necessary for positive results. These hormones can be present in your body for some time after pregnancy ends. So, if you were pregnant recently, there are chances that some residual hCG is still in your body. It can cause a false positive pregnancy test.

Faulty Test Kit 

Always check the expiry of the kit before buying. You should also ensure the device is working properly and is not faulty. You should prefer buying the equipment from trustable sources.

Reader’s error

Reading the kit’s results can be tricky. A novice person can misunderstand the results for a positive outcome. So, it is essential to read the instruction manual thoroughly to read the results correctly to get a correct positive pregnancy test. 

Ectopic Pregnancy

Sometimes, the fertilization takes place outside the uterus. It does not get the environment for growth but can release low levels of hCG hormones. This type of pregnancy can cause false results.

If you get positive results, it doesn’t always mean they are correct. Confirm the results before getting your hopes high.

Chances of a False Positive Pregnancy Test

As you know, the inaccurate results chances may vary due to different causes. But, the chances of false results are generally quite low. The risk of getting wrong outcomes is 1-2% only. You should not be too cautious about this matter, as false test occurs under specific situations. Try to eliminate all the potential causes, and you will likely get the correct results.

If you get a positive result but have doubts due to some diseases or medications, you should consult a professional first. He may do further tests on you to find out about the correct status of your results. 


What not to do before taking a pregnancy test?

Checkout the following tips to know what you should not do before the test:

  • Do not drink fluids excessively before taking the test. These fluids can reduce the concentration of hCG hormones in the body and cause false results.
  • If you take the pregnancy test too early, you may not get the results. The implantation time is 6-12 days after sex. So, you should wait and take the tests after 12 days.
  •  Make sure the testing kit is not defective. Purchase your kit from a trustable source so it doesn’t work inaccurately. You should also not use it after the equipment is expired. It won’t give you any results but can also be harmful. 
  •  If you are suffering from some diseases, then your doctor will run more tests on you. These tests will confirm if your pregnancy tests are right or not. So, you should contact your doctor in such cases.

Can you get a false positive pregnancy test before your period?

The chances are low that you get a false pregnancy result before your period but it is possible. So, if you want the best results, get rid of all the factors of a false test. 

Can you take a pregnancy test in the afternoon?

Getting a pregnancy test in the afternoon is perfectly fine. You will get pretty accurate results at this time as well as hCG levels remain normal the whole day. However, the best time for this test is morning, as hCG levels are highest at this time.

What drugs can cause a false positive pregnancy test?

Many drugs can contribute to a false test. Here is a list of certain types of drugs that can cause wrong outcomes.

Medications with hCG hormones.

  1. Antipsychotic drugs.
  2. Drugs containing the luteinizing hormone.
  3. Medications for hormonal therapies.
  4. Medications for many types of cancer.
  5. Some allergy treatment medications.
  6. Antidepressants.

What infections can cause a false positive pregnancy test?

Infections may cause other harm but they do not mess up your pregnancy tests. However, many infections are responsible for producing hormones known as hCG. As we know, the testing kits detect these hormones for positive results. It means you may get a false positive result. These infections are as follows:

  1.  Trophoblastic disease
  2. Urinary tract infections
  3. Ovarian cysts

Keep in mind a false test always has a very low chance. But it only takes a little to schedule sessions with your doctor. 


In a nutshell, the presence of sperm has nothing to do with the positive pregnancy test. But there are other factors that can ruin your pregnancy test. You must know all medications, infections, conditions, or any other cause of a false test. Also, you should know how pregnancy works to interpret the results better. Again, the chances of a false positive pregnancy test are generally very low. But, it is better to be cautious and stay in contact with a professional.

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Maria Gonzales, M.Ed., expert in child development and founder of, merges academic insights from Michigan State University with real-life parenting wisdom. Certified in Precision Nutrition and Child Development, she offers invaluable advice on nutrition, communication, and education for parents and parents-to-be.

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