Human chorionic gonadotropin (hCG) is a special “pregnancy hormone”. It is produced after fertilization (5-6 days from the moment of fertilization) by the envelope of the embryo, which is called the chorion. Consequently, the presence of a chorionic tissue in the body indicates the onset of pregnancy. Having determined the level of hCG, you can get the most accurate and reliable information about the presence (or absence) of pregnancy at a short time. Also, hCG level helps diagnosing a normal and pathological pregnancy. That’s why it is so important to know hCG levels in pregnancy.
hCG Analysis during Pregnancy: Normal and Pathological Values
HCG during pregnancy is produced in the body of absolutely all future mothers. It is a hormone that is produced by the cells of the chorion immediately after the implantation of a fertilized egg. In some cases it is very important to know hCG levels in pregnancy to prevent spontaneous miscarriage, to suspect ectopic location of the fetal egg, a frozen pregnancy, etc.
How Is hCG Determined?
The content of chorionic gonadotropin can be checked with the help of blood, urine, and pregnancy test. The blood test is considered the most accurate. With the help of it you can determine the increase of hCG 4-5 days, and even earlier, after the implantation of the oocyte. Even before the onset or delay of menstruation.
The urine analysis is less accurate. A pregnancy test is even less reliable. Still, most women use pregnancy tests because of their convenience. Tests show the exact result from the first day of the delay in menstruation. However, some particularly sensitive tests can show the result 2-3 days before the expected date of the onset of menstruation.
Why Is It Important to Determine the Level of hCG in the Blood?
There are at least two reasons for this:
- The analysis on hCG allows to confirm or deny the onset of pregnancy and
- to suspect deviations in the current pregnancy.
A test for the presence of hCG in the urine is used in pregnancy tests. By analyzing the blood, you can determine not only the presence, but also the exact value of hCG, which is more important and indicative.
A blood test for HCG allows you to diagnose pregnancy a few days earlier than usual pregnancy tests, that is, approximately from the 5th to the 6th day after conception. Further, depending on the hCG levels in pregnancy, one can judge whether pregnancy progresses normally, or there are deviations.
During the first weeks hCG concentration doubles every 1-2 days. The hormone reaches its maximum by 10-11 weeks. Then the level of hCG in the blood begins to decrease smoothly. This happens when the placenta begins to work independently and takes on the function of the hormonal center.
HCG is a component of a double and triple screening test, which is performed at 10-11 and 14-15 weeks. It helps identify possible deviations in child development and hereditary anomalies.
When determining hCG by weeks, doctors orient in the following way:
- the indicator less than 5 mIU / ml is considered negative;
- the indicator from 5 to 25 mIU / ml – is doubtful and requires a repeated test in a few days;
- when assessing the deviation from the norm of HCG by weeks, a difference in excess of 20% of the norm is taken into account. Increase or decrease in the level of hCG by 50% or more is considered a pathology.
Deviation by 20%, as a rule, requires a repetition of the analysis. If a further deviation from the norm is found during the re-examination, this may indicate the presence of the pathological process. But if the result remains the same, and the clinical picture of complication of pregnancy is absent, elevated hCG is considered as a variant of the individual norm.
A single study of the level of hCG is rarely performed. It is only relevant for early diagnosis of pregnancy. To detect pathological conditions (threat of interruption of pregnancy, fetoplacental insufficiency, etc.) doctors observe the dynamics of changes in hCG levels in pregnancy.
HCG Levels in Pregnancy
hCG levels in weeks from LMP (gestational age):
Non-pregnant females: 0 – 5 mIU/mL
Postmenopausal females: 0 – 8 mIU/mL
3 weeks LMP: 5 – 50 mIU/mL
4 weeks LMP: 5 – 426 mIU/mL
5 weeks LMP: 18 – 7,340 mIU/mL
6 weeks LMP: 1,080 – 56,500 mIU/mL
7 – 8 weeks LMP: 7, 650 – 229,000 mIU/mL
9 – 12 weeks LMP: 25,700 – 288,000 mIU/mL
13 – 16 weeks LMP: 13,300 – 254,000 mIU/mL
17 – 24 weeks LMP: 4,060 – 165,400 mIU/mL
25 – 40 weeks LMP: 3,640 – 117,000 mIU/mL
The hCG levels in pregnancy are very variable. The initial increase happens due to the intensive growth of the fetus, the child’s place and active hormonal restructuring of the female body. At this time, the chorion releases a large amount of hCG to prepare the baby’s place and ensure the conditions for its successful development. But after 10 weeks the placenta undergoes significant changes. Now it is not so much a hormonal organ as a respiratory and nutritious one. Because it is due to the placenta the fetus receives nutrients and oxygen. This explains the decrease in the growth of hCG in the blood.
The amount of hCG in the blood gives information about the pregnancy and the health of the baby. HCG levels in pregnancy can indicate the following:
- The presence of multiple pregnancies (for example, twins or triplets). HCG levels are usually much higher when there is more than one fetus.
- Loss of pregnancy (miscarriage) or risk of miscarriage.
- Ectopic pregnancy – where the fertilized egg implants in the wrong place.
- Problems with the growth or development of the baby.
- Abnormal tissue growth in the ovaries or uterus, including some types of cancer in women who are not pregnant.
Low HCG Levels in Pregnancy
Reducing the level of hCG in comparison with the norm for this period, can talk about a few things:
- incorrectly exposed term of pregnancy;
- pregnancy ceased to develop;
- ectopic pregnancy
- threat of spontaneous miscarriage;
- delay in fetal development;
- prolonged pregnancy;
- abnormal function of the placenta;
- in the second and third trimesters, a decrease in the level of hCG may indicate fetal death.
In most cases, for the right diagnosis, apart from HCG analysis, you need to have at least another ultrasound and a second hCG analysis.
Increased hCG Levels during Pregnancy
Normally, the level of hCG in the blood increases approximately in 2 times every 2 days in the first 10 weeks of pregnancy. That is, for each period the content norm is different.
In addition, with multiple pregnancies, the level of hCG is even higher. This increase is completely normal.
Doctors state an abnormal increase of hCG when it does not correspond to the period of pregnancy. This can happen in several situations:
- incorrectly determined gestational age;
- the use of synthetic hormones during pregnancy;
- some diseases of the mother: diabetes, late toxicosis;
- multiple malformations and hereditary diseases of the fetus.
HCG Levels in Ectopic Pregnancy
With ectopic pregnancy hCG increases slower than with a normal one. This is one of the main criteria. The rule “twice in two days” is not fulfilled. For an accurate diagnosis, the test should be done at least 2 times.
In some cases, with an ectopic pregnancy, hCG may in general be negative.
HCG and Miscarriage
Decrease in the level of hCG in the blood is one of the main criteria of a threatening, or already occurred miscarriage. Unlike ectopic pregnancy, when hCG hardly increases from the very beginning, with a threatening miscarriage at the beginning indicators are normal. But as the death of the embryo and cells of its shells that produce hCG occurs, the level of the hormone begins to fall. The fall of it at the same time is constant and not less than half of the norm for a given period.
False Positive Result of HCG Analysis
Sometimes, chorionic gonadotropin is found in urine and in blood of not pregnant women, and even in men. And this is a very disturbing symptom. Possible reasons are the following:
- Molar pregnancy and choriocarcinoma;
- Seminoma and testicular teratoma (testicular tumors in men, more often – malignant);
- Neoplasms in the stomach and intestines (more often malignant);
- Neoplasms of the uterus, kidneys and other organs;
- After an abortion (within a week, as a rule);
- When taking medications containing chorionic gonadotropin (may be required, for example, in the preparation for IVF).
Thus, the analysis on hCG is applied for detecting missed miscarriage and ectopic pregnancy, as well as diagnostics of many oncological diseases.
How Accurate Is hCG Blood Test?
HCG blood test is the most reliable method of determining pregnancy. However, any study does not exclude errors that are allowed due to the human factor – violation of the rules by the patient or laboratory assistant. Women who have had problems with childbearing for a long time or took a number of drugs should report this before conducting the study. The fact is that such issues can distort the result of the analysis.
According to statistics, 2% of women who made a HCG blood test, got a false positive result of pregnancy. This may be evidence of hormonal failure or the presence of cancer. It also happens that during a confirmed pregnancy the analysis shows a negative result. This happens if ovulation or fetal implantation occurred later than usual or in the case of an ectopic pregnancy.