How does the pregnancy test work?
Most often, the maturation of the egg occurs in the middle of the menstrual cycle, that is, on day 14 with a cycle duration of 28 days. Fertilization can occur within 3-4 days. Then, if fertilization has occurred, the egg moves for 5-6 days along the fallopian tube, for some time it is in a free state, about 6-7 days. Then it is attached to the wall of the uterus and begins to develop and release the so-called hormone of pregnancy (human chorionic gonadotropin (hCG)), and it is determined in the woman's urine. The excretion of chorionic gonadotropin with urine begins from the second week of pregnancy in a small amount and is increased thousands of times by the twelfth week. Accordingly, the definition of pregnancy test can be reliable, at best, not earlier than two weeks after the onset of pregnancy.
Types of tests and ways to use them
Before use, you need to read the instructions for the test (leaflet), but all rapid pregnancy tests are based on the same principle, as mentioned above on the determination of the hormone hCG in urine, and doctors recommend using urine collected in the morning. There are three types of tests to determine pregnancy: a test strip, a flatbed test and an inkjet test cassette.
Test strip
It is necessary to select urine, vertically lower the test in a container with urine to a specified level (the dive time can be different usually 20-30 seconds). Afterwards, the test must be removed and placed on a horizontal surface.
Tablet test
It is necessary to put the cassette on a horizontal surface, draw a small amount of urine into the pipette and add 4 drops to the round hole on the cassette.
Inkjet test cassette
Before use, open the bag and remove the cassette. Part of the test-cassette marked with an arrow must be substituted for a stream of urine, after it is closed with a protective cap.
The results of all these tests are the same, if one strip shows up on the test - then you are not yet pregnant, if two - then you will soon become a mother. The result, as a rule, is determined in 3-5 minutes, but not later than the time specified in the leaflet.
Accuracy of pregnancy test
Modern express tests are accurate enough, up to 100%, however the most reliable results can be obtained only after the start of the delay. Although the error of the test can be quite high, the reasons for this may be as follows: the test may be overdue or spoiled; stale urine; a large amount of consumed liquid or diuretic drugs, which reduces the concentration of hCG; the test was conducted too early. Unfortunately, the express test gives a positive result both in ectopic pregnancy and in the threat of miscarriage (however, this is also observed in the determination of pregnancy by the study of hCG in the blood).
In any case, a more reliable result of the determination of pregnancy is the passage of an ultrasound procedure or examination by a gynecologist.