Beta hCG or bhCG is the acronym used for a hormone called human chorionic gonadotropin, whose blood dosage is widely used as a pregnancy test. The dosage of the beta hCG is a method with high accuracy for the diagnosis of a pregnancy.
When harvested at the right time and interpreted correctly, it has a very high success rate. The beta hCG may be obtained from blood tests or urine.
The human chorionic gonadotropin is a hormone important and necessary for the maintenance and development of pregnancy. It is produced by the trophoblast, an embryo cell group which gives rise to the placenta.
About 6 days after fertilization of the egg by sperm, the embryo formation comes to the uterine wall and lodges it. From this moment, the hCG hormone produced by the trophoblast can reach the mother's bloodstream, it can already be detected by ultra-sensitive laboratory tests.
As the embryo and the placenta will develop more hCG is being produced and released in the maternal circulation. In the first weeks of pregnancy, hCG levels double every 2 or 3 days. If the first 30 days of pregnancy the rate of increase in human chorionic gonadotropin is clearly little high, there may be something wrong during pregnancy, as fetal infeasibility or ectopic pregnancy.
As ovulation usually occurs about two weeks after menstruation, and after fertilization of the egg, the embryo still takes another week to reach the uterus, this means that even the most modern and sensitive tests, at best, only They will be able to detect bhCG the maternal circulation three weeks after the last menstrual period.
Usually, we gestation time from the first day of the last menstrual period, so current techniques can only detect hCG from the 3rd week of pregnancy.
In general, the hCG values are as follows throughout the weeks of pregnancy:
Nonpregnant women or less than 3 weeks of pregnancy: Less than 5 mIU / ml
3 weeks pregnancy: Between 5 and 50 mIU / ml
4 weeks pregnancy: between 5 and 426 mIU / ml
5 weeks of pregnancy: between 18 and 7340 mIU / ml
6 weeks of pregnancy: between 1,080 and 56,500 mIU / ml
7 to 8 weeks of pregnancy: between 7,650 and 229,000 mIU / ml
9 to 12 weeks of pregnancy: between 25,700 and 288,000 mIU / ml
13 to 16 weeks of pregnancy: between 13,300 and 254,000 mIU / ml
17 to 24 weeks of pregnancy: between 4,060 and 165,400 mIU / ml
25 to 40 weeks of pregnancy: between 3,640 and 117,000 mIU / ml
Please note that the above values are for guidance only. They are not a rule and other references may have different values. If your hCG is different, do not panic, this does not necessarily mean there is something wrong with your pregnancy. The most important is the speed of growth hormone in the first weeks.
The values of hCG for twin pregnancy, are twins or triplets, are usually higher because there are more gonadotropin production sources chorionic.
Usually, the peak bhCG occurs around the 10th week of pregnancy. The levels then begin to fall until the 20th week, during which stabilize, remaining more or less constant until the day of delivery.
If you notice the above given values, you will notice that there may be a huge variation between gonadotropin values human chorionic over the weeks of pregnancy. A pregnant woman in the 8th week may have a bhCG 9,000 and another with the same gestational age may have a bhCG 150,000. For this reason, the hCG values are not useful for determining the time of pregnancy.
If you are a careful reader, at this point should already be wondering why I sometimes write hCG and other write beta hCG (bhCG). After all, what is the difference between hCG and hCG beta?
HCG is a hormone composed of two large molecules, called alpha-subunit (or fraction alpha) and beta subunit (or beta fraction). The hCG alpha fraction is structurally similar to several other hormones such as follicle stimulating hormone (FSH) and luteinizing hormone (LH). Already the beta fraction of hCG is unique not exist in any other hormone. Therefore, to reduce the risk of cross-reacting with other hormones and hence the occurrence of false positives, research laboratories are the only beta fraction.
The hCG produced by the fetus passes into the bloodstream of the mother and is filtered by the kidneys and is eliminated in the urine of it. Thus, the beta hCG can be measured in blood and urine of women. Except for rare cases, which will be explained later, if you can detect bHCG in the blood or urine of a woman it is because she's pregnant.
There are basically two ways to evaluate the presence of bhCG: qualitative and quantitative bhCG.
The qualitative bhCG provides no values, just say whether or not human chorionic gonadotropin in significant amounts circulating in the blood in the mother. This medium is widely used in pharmacy pregnancy tests that use urine as the source for research. These tests only tell if the test is positive or negative.
The quantitative survey bhCG is the form used in most blood tests. In this way, the result is supplied in amounts, usually in milli International Units per milliliter (mlU / ml). In most laboratories, it is considered pregnancy values above 25 mIU / ml.
It is important to note that the urine pregnancy tests do not serve to establish the definitive diagnosis of pregnancy. Even when they are positive, it is necessary to confirm the results by examining blood, which is the most reliable pregnancy test.
Most blood tests can detect the minimum levels of BHCG 5 mIU / ml, but there are already supersensitive tests that detect the presence of up to 1 mIU / ml.
Most laboratories use the following benchmarks:
bhCG below 5 mIU / ml = negative, i.e. no ongoing pregnancy.
bhCG between 5 and 25 mIU / ml = undefined result. Generally indicates no ongoing pregnancy, but may be the case with very early pregnancy when hCG yet no time be sufficiently produced to be detected in the blood. In these cases one must repeat the test after three days.
It is always important to pay attention to laboratory reference values. In most cases, laboratories use a value of 25 mIU / ml as the limit. However, depending on the used chemical method, considered positive value may be lower or higher.
