Biological methods of diagnosing pregnancy are used in those cases when it is impossible to confirm or deny pregnancy based on clinical methods.
Hormonal (biological) reactions to pregnancy are based on the determination of the increased content of chorionic gonadotropin in the urine of pregnant women . The most common in recent years is the immunological method of diagnosis of pregnancy, which allows in the laboratory for 1.5-2 hours with high reliability (96-98%) to determine the presence of chorionic gonadotropin in the urine. The method is based on the reaction between the chorionic gonadotropic hormone of a pregnant woman with an antiserum. HCG is secreted by trophoblast, then by chorion, placenta and is released from the 7th to 8th day after fertilization, a positive reaction to hCG is also observed with bladder skeletons and chorionepithelioma, therefore this sign is likely.
There are one-time tests for the rapid and reliable determination of pregnancy by the presence of hCG in the urine. The test consists of an analytical plate, a glass for collecting urine, a pipette. For the analysis, you need to get a few milliliters of urine, which is collected at any time of the day. Before analysis, the analyte plate is removed from the sealed package and 3 drops of urine are applied to it. In the case of a positive reaction to hCG at the place where the urine was applied, the color of the plate changes from pink to purple in 3 minutes.
There are also methods for diagnosing pregnancy using animals. The Aschheim-Tsondek hormonal reaction is performed in mice weighing 6-8 g. It is also aimed at detecting chorionic gonadotropin in a woman's urine in the first weeks of pregnancy. The urine of a pregnant woman, introduced not to mature mice, causes the growth of uterus and ovarian follicles in these animals. When this reaction is formulated into urine according to the scheme (0.2-0.4 ml 6 times for two days), intramuscular injection is administered to mice. After 72 hours, the mice are opened and examined by the uterus and ovaries. The reaction is considered positive in the presence of uterine growth and hemorrhage into the cavity of enlarged follicles. The reliability of the method is 98-99%. A similar reaction can be put on sexually mature rabbits (Friedman reaction). The urine of the pregnant woman is then inserted into the vein of the rabbit ear, and the changes in the uterus and ovaries are determined after 48 hours.
Hormonal reaction on frogs (Halle-Mainini). Males of some frogs excrete spermatozoa under the influence of chorionic gonadotropin, which is contained in the urine of a pregnant woman. Urine the woman (2.5 ml) is injected into the dorsal lymphatic bag of frogs. After 1-2 hours, a liquid is collected from the cloaca with a glass pipette and examined under a microscope. The reaction is considered positive when mobile sperm are detected. The reliability is 98-99%.