Pregnancy tests: what they are and how they work
Searching for pregnancy is a process that can be more or less long, and different for each couple. But if there is a gesture common to anyone who is looking to conceive, it is to take a pregnancy test.
That wait, those nerves, those desire to see a positive. And also the disappointment when this positive does not arrive.
But “who” is responsible for these positive or negative results?
Yes. Pregnancy tests.
And the reality is that taking a pregnancy test is usually quite stressful. And it can be even more so if you are not sure how it works, what method to use and, above all, if you do not know the reliability of the results.
We are going to see exactly how pregnancy tests work, and how and when to use them and also what the best pregnancy tests are and their sensitivity.
At the end of the post you will see the different sensitivities of the tests and when to do the test to know if you are pregnant according to the sensitivity characteristics of the pregnancy tests.
But first... where do home pregnancy tests come from?
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The history of pregnancy tests
To know where (and when) home pregnancy tests appear we have to go back almost 100 years ago. We have always wanted to find out if there is a pregnancy, the good thing is that now we can know it very easily. Pregnancy tests have evolved a lot, of course, especially by increasing the sensitivity and reliability of pregnancy test results, we will tell you the details.
And in 1925 it was discovered that elevated levels of the hormone HCG (human chorionic gonadotropin) were, in some way, related to pregnancy.
And yes, this hormone is precisely the one that is measured in pregnancy tests to determine whether they are positive or not. But let's not advance events.
In fact, despite having discovered this implication of HCG in pregnancy, it was not until the 1970s that pregnancy tests began to be marketed through outpatient measurement of this hormone.
The first tests consisted of a complicated system with test tubes and the results took hours to arrive. Furthermore, these first pregnancy tests gave a high number of false negatives.
Starting in the 80s, pregnancy tests were developed that were somewhat more similar to those we know today.
The first pregnancy test - similar to the current one - that was marketed was the urine reagent strip with which, in just 10 minutes and with a little urine on the strip, clear information could be obtained. Of course, the tests were still not very sensitive, so it was usually necessary to wait until two weeks after the first absence to confirm the positive with guarantees.
Research to date has been aimed at improving the sensitivity of the tests to this HGC hormone. Thus, today, we find tests that offer reliable results from the first day of delay.
The evolution of pregnancy tests has led, especially in the last decade, to some digital tests, very easy to use, that are even capable of detecting the weeks of pregnancy we are in. And also, at a price that is quite affordable for most pockets.
⏰When should the test be performed?
The current reliability of pregnancy tests is high, although rush is often a bad advisor - as in so many other things in life.
In fact, Taking the pregnancy test too early could give us the wrong result.
Currently, the vast majority of pregnancy tests claim to be accurate from the first day of the absence of a period, or even before. However, more accurate results are usually obtained if you wait until after the first day that your period is due (or what is known as the first day of your missed period).
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Why wait to take a pregnancy test?
The wait to take a test to check for pregnancy has to do with the egg implantation process.
After sexual intercourse, if a sperm has managed to reach the egg and fertilization has occurred, the fertilized egg adheres to the uterine lining and implantation occurs.
This usually occurs about 15 days after fertilization, and the formation of the placenta also begins, in addition to the production of the human chorionic gonadotropin hormone (HCG).
Precisely this hormone is what pregnancy tests detect, but it is necessary for the hormone to enter the bloodstream, and from there it passes into the urine, where we can detect it thanks to current pregnancy tests.
As soon as implantation is consolidated, the concentration of the HCG hormone increases rapidly, doubling every two or three days. For this reason, the later you take the pregnancy test, the easier it will be to detect the positive. And vice versa, the earlier you take the pregnancy test, the more difficult it will be for the test to detect HCG because there will be a lower concentration of it.
The Most pregnancy tests detect the hormone from a concentration of 20 mIU/ml (milliInternational Units per milliliter of urine). Others pregnancy tests detect 10mlu/ml and the most sensitive 5mIU/ml that this is before the first fault.
Furthermore, and to understand the variability in the results of pregnancy tests, it must be taken into account that the time of ovulation can vary from one month to the next and the fertilized egg can implant in the uterus at different times. This moment directly influences the production of HCG and determines the moment in which it can be detected (that is, the moment in which a pregnancy test will give a reliable result).
If the cycles are also irregular, it is easy to make a mistake in calculating the ovulation date, so performing the test too early can end in a false negative, as well as a lot of disappointment.
When to take a pregnancy test to get a reliable result?
Although there are ultrasensitive tests that seem to detect the HCG hormone from the first week after conception, the most reliable thing is to perform a pregnancy test at least one day late in your period. However, if you take an ultrasensitive pregnancy test, you can do it even before your period is missed. We tell you everything about this in this post. PREGNANCY TEST BEFORE YOU MISS YOUR PERIOD
That said, and if your nerves allow it, the ideal would be to do the test one week after the scheduled date for the next spotting.
At what time of day should you take a pregnancy test?
Although the pregnancy test can be performed at any time of the day, it is recommended to use the first urine of the daya, which has a higher concentration of the HCG hormone, so it is best to do the test right after waking up with the first urine in the morning if you have not peed in the previous 3 hours.
If for any reason the test cannot be performed first thing in the morning, it is recommended not to drink too much water, this way the urine will be concentrated and the pregnancy hormone to be detected in the pregnancy test, also having more options to see the real test result and not have a false negative when there really is pregnancy.
Which test to choose depending on the time of testing?
Depending on when you intend to perform the test, attention should be paid to the maximum sensitivity level of the pregnancy test.
In a normal pregnancy, the pregnancy hormone or HCG can be detected in urine and blood only 7 days after conception. HCG levels continue to increase, exceeding 100 mlU/ml after the first absence and doubling their levels approximately every two days until reaching a range of 11,500-300,000 mlU/ml in weeks 10-12 of gestation, at the end of the first trimester.
From 7 to 10 days after conception there is a concentration of 10 mlU/ml or higher of HCG. This would be equivalent, in regular cycles, to 4-5 days before missed menstruation.
From 10 to 14 days after conception there is a concentration of 25 mlU/ml or higher. This would be approximately equivalent to the date on which your period should arrive. Most pregnancy tests have this standard sensitivity.
📌Types of pregnancy tests according to sensitivity to HGC
Pregnancy tests are super easy to use. The choice will be more in your sensitivity to clear up doubts and this is where It can be complicated to buy a pregnancy test and easily make the wrong choice.. Depending on their sensitivity, pregnancy tests could be classified into:
- Ultrasensitive test These tests detect a concentration of HCG from 5 mlU/ml. Example: LINK
- High sensitivity test: In this case, these are pregnancy tests that detect an HCG concentration of 10 to 15 mlU/ml. Example: LINK
- Sensitive test: Pregnancy tests with a sensitivity to detect HGC concentrations of 20 to 25 mlU/ml. Example: LINK
- Standard test: These tests allow HGC to be detected from a concentration of 25 to 50 mlU/ml. Example:: LINK
From the first day of missed menstruation, always assuming that these are regular cycles, all pregnancy tests have sufficient sensitivity to detect the presence of the pregnancy hormone.
Here I leave you the 2 tests that today are the best sellers and with greater reliability, which I warn you is also noticeable in the price:
Remember, if you want to know if you are pregnant, you can buy a pregnancy test online or at your pharmacy and clear up your doubts in less than 5 minutes. You just have to take into account the sensitivity of the pregnancy test and the time of day depending on the moment of the cycle or lack in which you find yourself.
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