The moment has come. We suspect that we are pregnant and want to confirm. Without errors. So, it's normal for us to wonder about the reliability of pregnancy tests.
Current pregnancy tests are very accurate if used correctly, however there are certain situations that can produce errors in the pregnancy test result. How and when can false negatives or false positives occur?
As we know, the mechanism of operation of pregnancy tests is the detection in the urine of the hormone called chorionic gonadotropin (HCG), which begin to secrete placental cells at the beginning of pregnancy.
HCG is a good indicator to know if pregnancy has begun because it appears in both urine and blood and also increases its concentration rapidly as pregnancy progresses.
Currently there are high sensitivity pregnancy tests, capable of detecting low concentrations of chorionic gonadotropin hormone in the urine.
However, in certain situations they can occur errors in the result of the pregnancy test, especially giving false negatives, although there are also less frequent cases of false positives. The most common mistakes in the pregnancy test are the following.
False positives in pregnancy tests
When a pregnancy test has a positive result, it has about 97% chance of success if it has been done correctly. However, there are certain circumstances that can give false positives.
- Some diseases, such as trophoblastic diseases and some cancers (gonadotropin-secreting tumors), lead to a high increase in the chorionic gonadotropin hormone, giving a falsely positive test result.
- There may also be a falsely positive result in women with hormonal disorders.
- Women who are receiving chorionic gonadotropin hormone as part of treatments to get pregnant may also see altered results with false positives.
- Sometimes due to the high sensitivity of the test, conception is detected in the first days of pregnancy. But some pregnancies end naturally in the first four weeks, thus giving what we perceive as a falsely positive result, although to speak more properly we would be facing a miscarriage.
- It is also a false positive if there is the case of ectopic embryos (those that occur outside the uterus or womb), when the chances of it coming to fruition are very low but HCG levels do rise. We remind you of the symptoms of ectopic pregnancy, as early detection is important to avoid serious complications.
- False positives for anembryonic or anembryonic pregnancies (without embryo), because although they raise the hormone levels, pregnancy is not real. We remember that it occurs when an egg that is fertilized and that after implantation in the uterine cavity, only the gestational sac develops but without developing the embryo inside.
False negatives in pregnancy tests
- If a urine sample is too diluted, it may not contain a representative level of the chorionic gonadotropin hormone. For this reason, in order not to obtain a falsely negative result, it is recommended to perform the test with the first urine in the morning, which has a higher concentration of the chorionic gonadotropin hormone.
- In the very early stages of pregnancyWhen the HCG is not yet detectable, a falsely negative result may occur. Therefore it is recommended to do the test after the delay of menstruation. If the result is negative but the menstruation does not appear, it is definitely not negative, and the test must be repeated after five or six days to confirm the correct result.
- If the use of the test is not correct, errors may also result. You should always read the leaflet containing all pregnancy tests carefully and follow the instructions. Wet the correct part of the test, expose it to the urine for the necessary time ... are some of the issues that we should not neglect. In case of doubt you should consult with the pharmacist.
As we see, pregnancy tests are not infallible. These we just saw are the most common mistakes of pregnancy tests. Ideally, wait for the test at the right time, use them correctly and in case of doubt perform a blood test or the relevant medical tests.
