Pregnancy Test Inaccuracies: False Negatives, Positives, and Secondary Tests

After a few days of mixed signals, taking a pregnancy test can be understandably nerve-wracking. And, the potential for an inaccurate pregnancy test brings this situation to a new level. While the modern pregnancy test is a huge leap forward in medicine with a complex hcG detection method, it is not flawless. Like several contraception methods, there are unfortunate situations in which the results of the pregnancy tests can be inaccurate. Fortunately, though, a qualified gynecological office can resolve these uncertainties with a thorough second pregnancy test. Read on to learn about how pregnancy tests can indicate false negatives, positives, and the various alternatives.


Are Pregnancy Tests Ever Incorrect?

There are occasions where the pregnancy test shows up as positive, and is incorrect. These situations are called “false positives”, and there are a number of reasons that they can happen.

  • Chemical Pregnancy: Chemical pregnancy is the term used to describe a very early miscarriage. Generally, this occurs if the embryo cannot implant early on. In most cases, women would not even detect a chemical pregnancy without a test. So, while it is true that the woman would be pregnant for a very short period of time, the pregnancy would end very early on.
  • Abortion: It can take a period of time for hormone levels to reduce after receiving an abortion, or experiencing a miscarriage.
  • Expired Test or Other Error: Failing to properly read the directions can result in a false positive pregnancy test as well. Taking a pregnancy test too early can indicate a false positive, as can taking a pregnancy test after drinking excessive water. Finally, use a non-expired pregnancy test, leaving it in the urine stream for the correct amount of time.
  • Evaporation Line: Depending on the brand and design of the pregnancy test, there may also be a second, faint line. This line, often called an evaporation line, will show up after the urine has evaporated on the pregnancy test. Following time directions is the best way to avoid confusion.
pregnancy test
  • Medication: Fertility-boosting medications can sometimes cause pregnancy hormones to be present. So, taking a test too early could trigger a pregnancy test false positive.
  • Ectopic Pregnancy: In simple terms, an ectopic pregnancy occurs when an egg is fertilized, but is not properly implanted in the uterus, and becomes stuck in the fallopian tube. The embryo produces hCG regardless, and may trigger a false positive.
  • Pregnancy Test False Negatives

    Pregnancy Test False Negatives

    False negatives are actually far more likely to occur than false positives. There are three main reasons that a pregnancy test could indicate a negative result, while the woman is actually pregnant:

    • Taking the test too early: It can be tempting to take the test after a missed period, especially if that has never happened before. But, it’s best to wait one week after a missed period before taking a pregnancy test, so that the hCG is detectable. Tracking your periods is one way to avoid confusion.
    • Checking test results early: It’s natural to be anxious to check the test results soon after placing the pregnancy test in your urine. But, for accuracy’s sake, be sure to allow the test to work for the designated amount of time.
    • Diluted Urine: As you go through the day, your urine will gradually become diluted through intaking various fluids. So, taking the test early in the morning is the best way to avoid this false negative.
    woman checking pregnancy test


    When’s the Best Time to Take a Pregnancy Test?

    It’s important to wait one week after the missed period to take a pregnancy test. If the period is late, then you will have taken a pregnancy test unnecessarily. Also, taking a pregnancy test early in the morning is the best way to ensure that the urine is not diluted. When your urine is more concentrated, the test can more accurately measure hCG.

    As we’ve discussed, improperly timing the pregnancy test could cause false results. Timing is crucial to ensuring that the test results are accurate, and if applicable, you are able to make an informed decision about receiving an abortion.


    Inconclusive Tests: Blood, Pelvic, or Sonogram

    Inconclusive pregnancy tests can stir up an understandable amount of confusion and stress for women. So, if you have a reason to believe that you are pregnant, then following up with a secondary test is important.

    Blood Test

    Blood tests examine the blood content of the woman, rather than the urine. They also test for hCG, the pregnancy hormone. And, there are actually two different types of blood pregnancy tests, both of which can generally offer a firm result sooner than others. Depending on your individual medical history, the gynecologist might recommend one over the other.

    • Quantitative Blood Pregnancy Test: This blood test measures the exact amount of hCG that is present in the blood. It can detect very low amounts of hCG, meaning that it is better at tracing pregnancy in various stages.
    • Qualitative Blood Serum Test: While it does not measure the amount of hCG present, quantitative blood tests determine whether or not it is present at all.
    • Pelvic Exam: Pelvic exams are not specific to pregnancy tests, and are actually performed regularly by gynecologists. During a pelvic exam, the gynecologist examines the various reproductive organs, as well as the external genitals. This is how gynecologists test for cervical cancer.
    pregnancy blood test

    Pelvic Exam

    Pelvic exams are not specific to pregnancy tests, and are actually performed regularly by gynecologists. During a pelvic exam, the gynecologist examines the various reproductive organs, as well as the external genitals. This is how gynecologists test for cervical cancer.


    Also called an ultrasound, this is a common way for gynecologists to examine a child’s development throughout the pregnancy. However, this investigative procedure doubles as a way to determine if a woman is pregnant.

    By applying gel on the abdomen, the sonogram can detect movement in the uterus through sound waves.

    sonogram pregnancy test


    Stony Brook Women’s Health

    If you believe that you might be pregnant, then you should take a pregnancy test. Doing so ensures that you can make the right decision– whether that is preparing for a child, or scheduling a surgical abortion procedure, or a medical abortion. Regardless of these factors, our experienced staff is here to help you through these times. Contact us for more information about pregnancy testing, or the abortion procedure.