Products
Pregnancy tests are commercially available as medical devices from various suppliers. They belong to the group of self-tests.
How it works
After implantation of the fertilized egg, the body begins to produce the pregnancy hormone human chorionic gonadotropin (hCG) in the so-called syncytiotrophoblast (later placenta). The concentration increases steadily at the beginning. The test detects this hormone in the urine. The test is performed with an antibody that binds to the hormone and with a color reaction (immunological test, immunochromatography). The specificity and sensitivity is usually above 99%.
Areas of application
With a pregnancy test, women can check for themselves whether they are pregnant. For example, due to a desire to have children or after unprotected sexual intercourse.
Implementation
The implementation depends on the product and the detailed instructions can be found in the instructions for use. General information is presented below. The Instructions for Use should be consulted before use. The test is usually performed at the time when menstruation would be due. There are also tests that can be used a few days before the due date. Urine is used for the test. From the due date it can be used at any time of the day, before that morning urine should be used, because hCG is concentrated in it. The test tip can be held directly in the urine stream. The urine can also be collected in a clean and dry (new) container. The test tip is immersed in the collected fluid.
Result and evaluation
After a waiting period, a control symbol appears in the control window to indicate whether the test worked. The evaluation may only take place if the symbol is displayed correctly and within the defined time period. A symbol appears in the result window indicating whether a pregnancy is present or not. This for example with a plus or minus sign. With digital tests, the result can also be displayed with words (e.g. “pregnant”, “not pregnant”). Some tests additionally allow determination of the week. If the result is positive, contact your gynecologist. In the practice, it is clarified whether a pregnancy is actually present. For this purpose, an hCG blood test or a sonography (ultrasound) can be performed, for example. Pregnancy tests can usually only be used once. Some packages contain two tests.
Precautions
Human chorionic gonadotropin is also used as a medicine and may falsify the result. Ectopic pregnancy, cysts, and conditions such as cancer can also cause a false positive result. False positive tests have been reported after the administration of phenothiazines. If the test is negative, pregnancy may still be present in some circumstances, for example, if testing was done too early, the hCG concentration was too low, or the test was used incorrectly. The test may be repeated after a few days or a week.
