It is believed that the first pregnancy test was invented in ancient Egypt. Many centuries ago, healers diagnosed conception if seeds of cereal crops sprinkled with female urine sprouted. Wheat sprouted – meant that there would be a girl, and barley – a boy. In the 60s of the 20th century, scientists repeated the test, establishing that its accuracy is 70%. He showed that fertilization had occurred, but did not determine the sex of the embryo. It was found that seed germination is associated with a high estrogen content in the urine of pregnant women.
Today, in order to find out about pregnancy, you do not need to experiment and wait a long time. Test strips in just 3-5 minutes give an answer whose accuracy is from 75 to 97% – it all depends on whether you follow the instructions.
A pregnancy test is a mandatory attribute of a female first-aid kit, many store it in case of delayed menstruation.
However, often even several test strips with a positive result cause girls in doubts about the correct diagnosis of pregnancy. We offer to understand how the tests from the pharmacy actually work, what they mean and whether they should be trusted? And can there also be a mistake in the test on which you found two strips?
How do tests work?
There are many tests for quick diagnosis of pregnancy, differing in cost and type, but the principle of work is the same for everyone. They reveal the special hormone hCG. Its production is activated in women exclusively during pregnancy. The fact is that hCG is formed after implantation of the fetus in the uterus and is secreted by the fetal membrane. The study determines the presence of a hormone in the urine or blood.
For home use, tests are offered in the form of strips that need to be dipped in urine. Laboratory tests that detect pregnancy in the first weeks are also used – a blood test for hCG. Of course, you can go to the clinic with a delay of menstruation, but most often there are enough stripes.
|Types of tests||How to apply|
|Strip||Dip in a container with morning urine, wait a few minutes – and you can find out the result. Suitable for home use only.|
|Jet||It is necessary to urinate for a test and expect the appearance of stripes. Research is convenient to do anywhere.|
|Tablet||Urine is collected from the container with the pipette included in the kit and dripped into the test window. The reagent indicator is protected by a case, which guarantees high accuracy.|
For complete confidence, you can purchase test systems of various types, but the result is usually shown in the form of strips. Basically, they work efficiently and give a reliable response 7-10 days after fertilization. In the pharmacy, you can also purchase studies with increased sensitivity to hCG.
Why two strips?
HCG in the urine is detected already on the 7-8th day, with the development of the fetus, its concentration increases significantly. Therefore, if pregnancy is suspected, you can immediately use an expert diagnosis and use the strips to find out the result. The most commonly used paper test, which is a paper strip. This is a kind of litmus that allows you to detect the presence of hCG.
On the surface of the test are strips:
- the first bar is a benchmark indicating that the test is suitable and its results will be correct;
- the second strip is a reaction to the content of the pregnancy hormone in the urine.
Testing begins with immersion of the open end of the strip in a small container with urine to the indicated mark. The fluid sequentially flows through 3 zones. The reagent applied to the surface of the test contains antibodies that are sensitive to the hCG hormone. If there is a pregnancy, then antibodies actively interact with urine and capture all the ingressing hormones.
An absorbent part with a coloring substance is provided on paper strips, which shows the test results. Coloring molecules activate enzymes that urine also carries on. In the second zone there is an even greater number of antibodies, and hormones settle here. Due to the dye particles on the strip, two bluish or reddish lines appear in the event of pregnancy. The last zone confirms the performance of the test. If no marks appear on the paper strip, it is considered to be expired or defective.
The test after immersion in the urine quickly takes on a certain shade. If pregnancy does not occur, there are no hCG hormones, so urine with enzymes passes freely, and the dye is not released. Two strips are visible if the girl is pregnant and a hormone is found in the urine. If only one band is present, then the result is negative, and there is no pregnancy.
Usually when placing the test in containers with urine, the first strip appears first, which indicates the reliability of the analysis. After sustaining the time specified in the instructions, you need to get the test and wait for the appearance of another mark. If you see two clear and brightly colored lines at once, then you have become pregnant. However, often the stripes look unclear or in doubt. So, a blurred and weakly pronounced strip does not give full confidence that the egg has been fertilized. In addition, a pregnancy test may be false. Reagents in stripes detect hCG only when it is sufficiently present in the urine.
|Second strip||Test value|
|Intensely colored||99% chance that fertilization has occurred.|
|Pale or fuzzy||A weak concentration of hCG hormones in the urine is possible, the test should be repeated after two to three days.|
|Missing||Conception did not happen.|
|Empty test without stripes||Defective sample or expired.|
A barely noticeable strip can appear in women in the first week of pregnancy, when the content of the hCG hormone in the body is still not high enough. You should also conduct rapid testing in the morning on an empty stomach in order to exclude impurities of various fluids drunk during the day. Confidence in the result will be given by repeated diagnostics using strips.
If conception has occurred, the amount of hCG hormone will double every three days. Usually, 10 days after fertilization, its level reaches a value of 25 units per ml – such an indicator and reagents are captured on strips.
Is a mistake possible?
There are times when a pregnancy test is wrong, especially if the study is done before the start of the delay. Most often, a false negative result occurs when fertilization has occurred, and only one strip has appeared. Two marks in the form of stripes may appear after an abortion, if it was not complete, or hCG is not yet completely eliminated from the body. The presence of two strips after menstruation also indicates the possibility of a miscarriage.
There are several factors due to which a pregnancy test shows the wrong number of strips:
- Low concentration of hCG in the early stages – if the egg is fertilized, the amount of the hormone will increase rapidly. On the first day of the delay of menstruation, it is too early to expect the appearance of two stripes.
- Violation of the instructions – you should strictly adhere to the time (4-5 minutes), collect urine in the morning, do not drink a lot of fluids the day before, observe sterility.
- Other sources of hCG in the body are undergoing treatment for infertility, taking certain medications, the presence of genital cancer, an ectopic pregnancy.