One of the most important laboratory studies in obstetrics is the analysis of hCG during pregnancy or the determination of a human chorionic gonadotropin in the blood.
It is a positive analysis of hCG in the early stages of pregnancy is an unconditional indicator of the successful fertilization of the ovum, the formation of the zygote, and then the blastocyst - with the introduction of the trophoblast into the endothelium of the uterus and the beginning of embryo development.
HCG - what is it?
HCG is a gonadotroph, a biologically active heterodimeric glycoprotein compound of more than two hundred amino acids, that is, a hormone that provides certain biochemical processes during pregnancy. In the composition of hCG two subunits - alpha and beta. The alpha subunit consisting of 92 amino acids is considered identical to such hormones as luteinizing (LH), follicle stimulating (FSH) and thyrotropic (TSH). And with the free beta subunit of chorionic gonadotropin (beta-hCG) consists of 145 amino acids and determines the unique properties of this hormone.
It is called chorionic because it is produced by the temporary organ of the embryo - its villous shell - by the chorion. The process of formation of the chorion from the trophoblast cells and the extraembryonic mesoderm of the inner blastocyst leaf occurs immediately after its attachment to the uterine wall.
After about a week, cells of the trophoblast of the chorion begin to produce chorionic gonadotropin, which interacts with the LHCG receptors of the embryo and helps maintain the yellow body of the ovaries before the 8th week of gestation. This is a very important function of hCG during pregnancy, since before the formation and beginning of the functioning of the placenta, another gonadotropic hormone is synthesized by the yellow body - progesterone, supporting pregnancy by suppression of ovulation, stimulating transformation of the endometrium and the formation of a network of capillaries.
In addition, due to its negative charge, hCG removes the immune cells of the mother from the embryo, preventing rejection of the fetus in the first trimester. Also, this hormone plays a role in the proliferation of embryonic cells. After their differentiation into types of tissues and complete formation of the placenta (during the fourth month of pregnancy), the synthesis of hCG takes on the placenta.
In 85% of pregnant women, the hCG level in the blood doubles every 48-72 hours in the first four weeks of pregnancy. The hormone is first found in the blood, and then in the urine.
When it is possible to do hCG analysis on pregnancy, and when the test for hCG shows pregnancy? It is possible to take an analysis of hCG in the early stages of pregnancy 12 days after the delay of the next monthly. A blood test will show the pregnancy 10-11 days after conception, and on the 12-14th day the hormone can be detected in the urine.
Although the levels of hCG in urine are usually lower than in serum, the excretion of the hormone by the kidneys is used in fast test strips. Answering the question, what is more reliable - an analysis of HCG or a pregnancy test? - Obstetricians-gynecologists emphasize the higher sensitivity of hCG analysis in the blood. This means that when examining a blood sample, you can establish the fact of pregnancy several days earlier than using a test.
In addition, if a woman's pregnancy test is used a short time after the alleged conception, when the level of hCG, including urine, is not high enough, a false negative result is obtained. See also - Pregnancy test at home