False Negative Pregnancy Test: 5 Reasons It May Happen

Dr. Sheila Sedicias
About the author: Dr. Sheila Sedicias
July 2021

Home pregnancy tests are very trustworthy if done according to the packet instructions and at the right time, i.e. the first day after the period is due and onwards after that. However, to confirm the result, the best thing to do is repeat the test three to five days after the first result.

Even though the tests are very trustworthy, many times there are unexplainable changes in a woman’s menstrual cycle, which can cause doubts, especially when the pregnancy test is negative, but your period still doesn’t come.

So, we put together some causes that can lead to a false negative, which is when the expat mother is in fact pregnant, but the test comes back negative. It’s important to remember that the best way to confirm a suspected pregnancy is to go to the gynecologist to do a blood test and measure bHCG hormone levels.

1. Precocious pregnancy test 

This is the main reason for a false negative test and it happens when you suspect you are pregnant, and have some symptoms, which you believe are the first signs of pregnancy, such as painful breasts, so you do the test as soon as possible.  

However, the best way to guarantee a correct result is to wait for your period to come late, and then to do the test a few days later, so the body has time to produce the bHCG hormone in sufficient quantity to be eliminated through urine and detected in the pregnancy test.

2. Irregular menstrual cycle 

When your menstrual cycle is irregular, it is also more probable that the pregnancy test will come back negative. This usually happens when the test is done before the menstrual delay and your period is simply a bit later than usual.

So, the best way to guarantee a correct result if you have an irregular cycle, is to only do the test two to three weeks after you predict your period would come. 

3. Ectopic pregnancy 

An ectopic pregnancy is quite a rare condition, in which the fertilized egg implants outside of the uterus, usually in the fallopian tubes. In these cases, the body takes longer to produce the bHCG hormone, and so the result can be negative even if fertilization happened.

This type of pregnancy is a medical emergency that should be interrupted as soon as possible, as it can cause serious damage to the woman’s reproductive system. A few signs that can indicate a possible ectopic pregnancy are intense stomach pain, vomiting, vaginal bleeding, or heaviness. If you have these symptoms, please go to the hospital to confirm the diagnosis and carry out an abortion if it is the case.

4. Breastfeeding

When a woman is breastfeeding, the body regulates slowly along time, especially in the production of hormones. Therefore, it is possible for a woman’s cycle to be irregular initially, even though she used to have a regular cycle before.

For that reason, some women may think they are pregnant, when their period is late. So, it is possible for the pregnancy test to be negative.

5. The test has expired 

Even though this is rarer, it is possible that the pregnancy test has expired. When this happens, the reagent used to identify the presence of the bHCG hormone is not working properly, giving a false negative result.

So, it is very important to check the expiration date on the packet before using it. Additionally, if pregnancy tests are not stored propely, even though they are within the expiry date, they may not give an accurate result. For those reasons, if you suspect that the test is not giving the correct result, you will need to buy a new one. 

What can cause menstrual delay

When a pregnancy test is done properly at the right time and it has even be repeated, but the result is negative and your menstruation still does not appear, it is probable that you are not pregnant. This is because there are many factors that can cause a delay in menstruation that are not a pregnancy.

Some of these causes are:

  • Excess stress and anxiety;
  • Practicing intense physical exercise for a long time;
  • Thyroid problems;
  • Very restrictive diets.

Therefore, if your menstruation is late and you do not have a positive pregnancy test result, the best thing to do is to visit a gynecologist to identify whether there is another cause that may be leading to this delay, and then start the right treatment.

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About the author:
Dr. Sheila Sedicias
Physician graduated in Mastology and Gynecology by UFPE in 2008 and member no. 17459 of CRM-PE, Brazil.