Pregnancy can be confirmed by a blood or urine test for the presence of human chorionic gonadotropin. This hormone is produced by the blastocyst (a fertilized egg in the next stage of division) after implantation in the uterus and in the placenta villi. The goal of the hormone is to support the production of progesterone in the corpus luteum of the ovary, which is necessary for the development of the fetus. It must be borne in mind that increased hCG during pregnancy may indicate some abnormalities in the development of the fetus. In men, as well as in non-pregnant women, the presence of hCG in the blood may indicate testicular or ovarian cancer and other types of oncology.
As a rule, the level of gonadotropin in the blood below 5 mU / ml is considered negative, that is, the absence of pregnancy. A result above 25 mU / ml is considered positive and indicates that the woman is pregnant. Since implantation of the embryo can occur at different times after ovulation (on average ten days), therefore, the growth of hCG during pregnancy begins a few days after fertilization.
An embryo that moves through the fallopian tube into the uterus consists of an embryonic node (a cluster of cells) and an surrounding layer known as trophoblast. This is where the production and secretion of gonadotropin begins, which reaches the ovaries, where it stimulates the newly formed corpus luteum to produce progesterone.
The chorionic hormone gonadotropin can be detected using blood and urine tests. A blood test can detect the presence of hCG and accurately determine the amount of hormones. This test can be used to determine if a woman is pregnant, if the baby is developing normally, or if an increased level of hCG is associated with cancer. The level of the chorionic hormone gonadotropin is often taken into account when screening for birth defects. This test is usually performed between the 15th and 20th week of pregnancy. In addition to blood, a urine test is also performed. This test does not provide accurate measurements of hCG levels, but shows the possible presence of the hormone. Urine for analysis should be collected immediately after waking up, because in the first portion the level of hCG is the highest.
At the beginning of pregnancy, hCG is very low, and only with the passage of days its concentration will double approximately every 48 hours and will reach its maximum at 7-12 weeks, after which it will slowly decrease. The concentration of hCG should be doubled every third week of pregnancy. When the value reaches 1200-6000 IU / ml, growth will occur every 96 hours. Very high hCG in pregnant women may be associated with pathology of placental tissue, or indicate the occurrence of choriocarcinoma. In addition, increased hCG during pregnancy may be the result of multiple pregnancy. An abnormal increase in the level of gonadotropin can also occur in the case of an ectopic pregnancy, with congenital defects in the development of the child or miscarriage.
It is increased hCG during pregnancy that is a symptom of molar pregnancy. As a result of a genetic error, after fertilization of the egg, abnormal cell growth begins in the form of blisters in the placenta. And although a woman may have the usual symptoms of pregnant women, such a chromosomal abnormality is extremely dangerous, as it can develop into a malignant form.
It should be remembered that increased hCG during pregnancy can cause nausea and vomiting. Unfortunately, such an etiology is not fully understood. But most often, an abnormal level of hCG occurs in women before 20 and after 35 years.
Of course, you should not compare the level of hCG in different pregnant women at the same time. Its concentration can be quite different, vary throughout the entire period of bearing a baby and depend on the state of health and lifestyle of the woman herself. Most importantly, when hCG is in the normal range and increases over the course of weeks.