Every day thousands of women in the world take a home pregnancy test, of those that can be bought in pharmacies and that announce us, usually with the appearance of some lines, after detecting urine, whether we are pregnant or not. But, How do pregnancy tests work? How reliable are they?
The operation of the pregnancy test is very simple. Although externally there are differences, inside these sticks, one of whose ends must be impregnated in urine, there is a reactive absorbent strip that detects the presence of chorionic gonadotropin hormone (HGC) in the urine, that is, the pregnancy hormone .
We must bear in mind that urine pregnancy tests will only be positive when there are sufficient levels of HGC hormone in the blood, so at the beginning of pregnancy a test can be negative and yet we are pregnant. In general, with a level of HGC level below 25-50 mlU / mL (International units per milliliter of urine), the test will be negative.
As the level increases if the urine is more concentrated, Many tests recommend that the test be done with the first morning urine. If not, it is enough to wait a few days to perform the test (remember that it is recommended to do the test when there is a delay in menstruation for regular cycles) so that pregnancy hormone levels have increased and are detected by the test.
Reliability of pregnancy tests
In general, urine tests require 20 to 100 mIU / mL of pregnancy hormone concentration to test positive, depending on the brand. Blood tests detect the hormone with much lower concentrations, so they are more reliable even before the first lack of menstruation.
Pharmacy tests have a reliability of between 75 and 97 percent if the result is negative, while if the result is positive, the reliability is greater: 99 percent. Remember that a urine test can give us false positives or false negatives.
The process to perform the test is simple. Once the "stick" has been unwrapped, the cover that protects the test strip that we impregnate in urine is removed. It is recommended to wet it directly when urinating (for a few seconds), and then cover it again, without coming into contact with any other substance, and wait a few minutes leaving it on a flat surface.
After three to five minutes we can read the result, which will be indicated in a different way according to each brand sold. That is why you have to read the instructions in each case. The most common is that in a small window of the stick two lines appear to give a positive. There are also other digital systems that give us a more complete reading, and can even indicate the week of pregnancy if it is a positive.
After know how the pregnancy test works, we only have to perform the test correctly (if no hairline or signal appears we will have made a mistake) and good luck!
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