Some 20 years ago, confirmation of pregnancy required a wait of 2 to 3 months before the doctor could confidently congratulate the patient on the upcoming replenishment. Modern women find out that sometimes they are pregnant even before they have a delay, thanks to a test that showed the cherished two stripes.
All commercially available pregnancy tests work on the same principle. The reagents in them interact with a certain hormone called human beta-choriongonadotropin, or simply hCG. The production of this hormone begins almost from the first day after conception and is necessary for the accelerated formation of two other hormones - estrogen and gestagen, which are required to maintain pregnancy.
Before use, the test usually looks like a regular strip of cardboard, in most cases it is enclosed in a plastic container with windows for convenience. One end of the strip is designed to be held in the hand and the other to be dipped into the urine being tested. Some models come with a pipette, which should be used to collect urine and apply a few drops to a specially designed opening. After the test has been "soaked", the most interesting and crucial moment comes. The urine moves up the dough, passes through the strip with the reagent applied and a little later through the so-called control strip. The control strip should turn red, and on some tests it is possible to turn blue anyway. It will appear even if you test the test on compote or clean water. Its purpose is to show that during storage and transportation of the dough, all the necessary requirements have been met to preserve its quality. But if the control strip does not appear, this is considered a reason to discard the test immediately. You cannot believe the testimony of a spoiled test.
The next strip in the path of the test liquid is the reagent strip. In the presence of a certain concentration of hCG, it acquires the color declared in the instructions for use, most often red or pink. The longer the gestation period, the more intensely colored the strip will be, but even if it remains rather pale, the test can be considered positive. That is, a positive test should ideally have two stripes that appear: test and control.