Can a test fail to diagnose pregnancy when it is present?

Women frequently use home pregnancy tests to determine whether they are pregnant. Even in situations where pregnancy is present, these tests may yield a negative result. For those attempting to conceive, this can be perplexing and concerning.

A test’s inability to identify pregnancy can be attributed to a number of factors, including improper testing procedures or defective equipment. By being aware of the variables that could impact the accuracy of the outcome, one can prevent needless anxiety and make sure the right actions are done in the future.

This post will discuss the causes of false negative pregnancy test results and offer advice if you think you might be pregnant even after receiving a negative result.

Principle of operation

Manufacturers of all pregnancy tests without exception use the same technology – test systems of any type (strips, tablet and inkjet, digital) determine in the urine an increased level of a special, unique hormone of pregnant women – human chorionic gonadotropin. As soon as the level of this hormone in the urine begins to exceed the sensitivity threshold of a certain test, the test zone, to which the reagent sensitive to hCG is applied, is colored, this is the same second strip indicating a positive result. Where does hCG come from, how does it increase – let"s consider in more detail. Human chorionic gonadotropin is present in the blood in small quantities in men and women outside of pregnancy. Its content is usually so small that it is almost not given significant diagnostic value – from 0 to 5.0 mIU / ml.

Because tests are unable to identify such a quantity, women who are not pregnant do not see a second strip on the testing apparatus.

In the first days after fertilization (within 7-9 days), the embryo moves along the fallopian tube, descends into the uterus and gradually begins the implantation process. First, it goes through the adhesion stage (sticking to the wall of the uterus), and then the villi of the outer layer of the fertilized egg begin to produce a complex enzyme that dissolves the cells of the endometrium. This is how a depression is formed, into which the embryo is comfortably immersed. The villi of the chorion connect with the mother"s blood vessels. From the mother"s blood, already on the 7-9th day after ovulation, the future child begins to receive the substances and oxygen it needs. And the villi begin to produce hCG in high doses, while the concentration of the hormone in the blood grows quite quickly – every two days it doubles.

Why is this necessary, you ask. On the ovary after ovulation, in the place where the follicle with the egg was, a temporary endocrine gland appears, which is called the corpus luteum. It produces progesterone – a hormone necessary for the proper functioning of the female body in the second phase of the menstrual cycle and in the early stages of pregnancy before the formation of the placenta. If there is no pregnancy, the corpus luteum regresses and after 10-12 days after formation stops producing progesterone and is absorbed. The hormonal background changes, and menstruation begins. When pregnancy occurs, progesterone softens and increases the thickness of the endometrium to facilitate the task of implantation, reduces the tone of the uterus, suppresses the aggressive immunity of the woman, which can mistakenly recognize the fetus as a foreign object and attack it, prevents the onset of menstruation.

  • Menstruation
  • Ovulation
  • High probability of conception

14 days prior to the beginning of your menstrual cycle, or on the 14th day of a 28-day cycle, is when ovulation takes place. Since there is often variance from the average value, the computation is imprecise.

In addition to using the calendar method, you can check cervical mucus, measure your basal temperature, use special tests or mini-microscopes, and test for progesterone, estrogens, LH, and FSH.

Folliculometry (ultrasound) can undoubtedly be used to determine the day of ovulation.

  1. Losos, Jonathan B.; Raven, Peter H.; Johnson, George B.; Singer, Susan R. Biology. New York: McGraw-Hill. pp. 1207-1209.
  2. Campbell N. A., Reece J. B., Urry L. A. e. a. Biology. 9th ed. — Benjamin Cummings, 2011. — p. 1263
  3. Tkachenko B. I., Brin V. B., Zakharov Yu. M., Nedospasov V. O., Pyatin V. F. Human Physiology. Compendium / Edited by. B. I. Tkachenko. — M.: GEOTAR-Media, 2009. — 496 p.
  4. https://ru.wikipedia.org/wiki/Овуляция

Up until the end of the first trimester, hCG levels rise. After the placenta assumes control of the endocrine system, the corpus luteum regresses naturally and hCG is no longer required to maintain it.

As a result, the tests’ basic idea is to determine whether high levels of hCG are present. Naturally, home use systems are unable to determine its precise quantitative content; a laboratory blood test is available to determine the level of chorionic gonadotropin.

However, the test has a high degree of accuracy in identifying the actual occurrence of a rise in hormone levels.

Optimal timing for testing

Failure to follow the diagnostics’ timing is one of the most frequent causes of tests failing to reveal pregnancy when it is there. Stated differently, women begin testing too soon, while the level of human chorionic gonadotropin is still low.

It is known that the uterine wall triggers the start of the active production of hCG immediately after the embryo implants, and that the hormone then doubles every 48 hours. That is, only 3–4 days after implantation, or 3–4 days before the anticipated start of menstruation, does the blood level of hCG first exceed the "non-pregnant" norms. However, it runs in the family. The substance is always present in lower concentrations in urine, which is why test manufacturers advise starting the test no earlier than the first day after the delay.

A lot also relies on the kind of test apparatus you select. Digital tests make mistakes far less frequently than strip strips, which are less accurate. However, when the hCG level is just starting to rise, strips can identify a second weak, pale strip; digital devices are unable to do this.

The sensitivity thresholds of various tests vary; the most sensitive tests have a label on the package indicating that their threshold is between 10 and 15 mIU/ml. Even if a fuzzy second strip is obtained three days prior to the anticipated menstrual date, these tests can detect pregnancy earlier. Under the right conditions, ultra-sensitive test systems can detect pregnancy, but you shouldn’t particularly rely on this.

The majority of tests that are most widely used by fair-skinned people have sensitivity thresholds between 20 and 30 honey/ml. It is unlikely that these tests will turn out positively before the menstrual delay, but most of the time they can provide a fairly accurate result—positive or negative—as early as the first day of the delay.

Consequently, the first day of delay should be regarded as the ideal time to begin self-diagnosis.

Don’t give up if the test reveals a very weak and pale second strip or fails to reveal a second strip and there are no menstrual periods as predicted. This does not necessarily mean that there is no pregnancy.

Reasons for a negative test after a delay

Rechecking is necessary if the test result is negative or slightly positive and there is a menstrual delay. Even though there are other reasons why menstruation might not begin, such as hormonal imbalance, ovarian dysfunction, or an inflammatory process, the mere absence of menstruation is an indirect indicator of a potential pregnancy. In this instance, the test will undoubtedly continue to be negative after 10 days, on the second and fourth days of the delay. Once two weeks have passed and there is no menstruation, you should see a gynecologist to have your reproductive health evaluated.

Remember to keep an eye on your wellbeing, but try not to overstate or seek out emotions that aren’t there. In addition, you should think about the potential causes of this phenomenon if your test results are still negative and you experience symptoms of a possible pregnancy, such as feeling sick in the morning, having swollen and sore breasts, or changing your sense of taste and smell, along with delayed period start.

Late ovulation and implantation

Not every woman uses an ultrasound or performs an ovulation test to monitor her period. Because of this, the majority of women are unable to pinpoint the exact day—plus or minus one or two—on which the egg was released and the resulting baby was conceived. However, the notion that ovulation always happens in the middle of the cycle is deeply ingrained in people’s thoughts and is something that women learn from the Internet.

This is a false impression. There are two types of ovulation: late ovulation, which can happen as little as one week before the anticipated menstrual period, and early ovulation, which happens before the 12th day of the cycle. This subtle and delicate process can be impacted by a number of factors, including hormonal disorders, hypothalamic-pituitary anomalies, inflammatory processes in the body, stress, workload, and chronic fatigue. A flight, a cold, the flu, or a business or vacation trip that involved a time zone shift or change in schedule can all impact ovulatory processes and cause a significant day in the female cycle to occur later or earlier.

We’re not going to discuss early ovulation. It usually results in an immature egg, making conception improbable, but in the event that it does, the test becomes "striped," recording 6-7 days prior to menstruation (many such examples with photos available online). The topic of late ovulation interests us. It is more frequent, and it causes the implantation to be delayed by seven to nine days.

It follows that when pregnancy occurs, it is not surprising that the test is still negative at the start of the delay.

Ovulation also happens later if it is only 4 days delayed, and by the anticipated day of the delay, not enough hCG has accumulated for the test to detect it.

There is late implantation when ovulation occurs on schedule. Doctors have not yet fully studied the mechanisms underlying this process, so it is unclear why some embryos start the adhesion stage as early as the fifth day after fertilization, while others float freely in the uterus for several days after passing through the fallopian tube and don’t start implantation until the ninth or tenth day of the cycle. Even in the unlikely event that conception occurs after the tenth day, implantation is unlikely to occur due to physiological changes in the endometrium brought on by the fading of the corpus luteum, which prevents the fertilized egg from being deposited into the endometrium.

Let’s try to figure out when an ovulation test that is performed 4-5 days late can yield a positive result. If, for example, ovulation only happens on the 18th or 19th day of the cycle rather than the 14th, which is a 28-day period, then implantation will typically take place on the 23rd or 25th day of the cycle, and the first test results will only be obtained 6-8 days after implantation, or a week after the delay began.

Ectopic pregnancy

Because of this pathology, the fertilized egg fixes outside of the uterus, in 97% of cases in the fallopian tube. The chorion also secretes hCG concurrently, but at a much lower concentration and with slower growth (dynamics). Because of this, in the event of an ectopic pregnancy, the test may be negative or only weakly positive (the second strip is dubious and extremely pale) after the delay has begun.

Frozen pregnancy at an early stage

In terms of the possibility of halting the development of the embryo, the obstetric standard states that the period between the last menstrual cycle and the third and fourth weeks of pregnancy is one of the most dangerous. This is an instance of a frozen pregnancy. hCG is either not produced at all after the embryo dies, or it is produced for a further two to three days at negligible concentrations. The human growth hormone level fluctuates quickly before starting to decline.

In this instance, if the embryo perished before the hormone concentration hit the test systems’ sensitivity threshold, the test might not produce a second strip at all, either before or after the delay.

In the event that sufficient hormone was produced prior to the baby’s death, the tests reveal a weak second strip that does not get brighter when repeated diagnostics are performed two or four days after the initial test.

Self-diagnosis errors

And lastly, a test error might be the cause. Carefully read the instructions. Avoid submerging the test tube below the control line, keeping it in urine for longer than the allotted amount of time, and waiting hours for the results. There is little chance of error if you follow the directions.

It is imperative that you verify both the test’s expiration date and the integrity of its packaging, as outdated tests are frequently inaccurate. Test the urine from the morning portion, which has the highest concentration. Avoid consuming liquids or foods high in liquid content for four to five hours prior to the test.

Reason for False Negative Explanation
Testing Too Early The body may not produce enough pregnancy hormone (hCG) early on to be detected by the test.
Test Sensitivity Some tests are less sensitive and may require higher hCG levels to show a positive result.
Improper Test Usage Not following the instructions, such as using diluted urine or testing at the wrong time, can affect results.
Expired or Faulty Test An expired or defective test may not give accurate results, leading to a false negative.

Although most pregnancy tests are accurate, there are instances when they don’t. Women may doubt the accuracy of the results due to factors such as timing, misuse, or health issues.

It’s crucial to not rely solely on a negative test result if there’s still a chance of pregnancy. Clarity can be obtained by retaking the test a few days later or by seeing a doctor for more precise testing.

You can better control expectations and make sure you move forward with the right decisions by being aware of how pregnancy tests operate and what might interfere with them.

Indeed, even in cases where pregnancy is present, a pregnancy test may fail to detect it. This can occur for a number of reasons, including testing too soon, using a faulty or expired test, or improperly following the directions. Moreover, particularly in the early stages, hormone levels might be too low for the test to pick up on. In situations like these, it’s advisable to retest a few days later or seek a doctor’s advice for a more precise blood test.

Video on the topic

SIGNS OF PREGNANCY | WHAT TO DO when the PREGNANCY test showed TWO stripes | Dr. Kruglov

PREGNANCY TEST | Can a pregnancy test be wrong

MY FIRST SIGNS OF PREGNANCY BEFORE A DELAY / why the test showed 1 stripe?!

📅 What can be associated with a delay in menstruation?

DELAY IN PERIODS AND THE TEST IS NEGATIVE | Delayed menstruation

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Elena Ivanova

Mother of three children, with experience in early development and education. Interested in parenting methods that help to reveal a child's potential from an early age. I support parents in their desire to create a harmonious and loving family.

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