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HCG during pregnancy

HCG during pregnancy


Most women take an hCG test for the first time when pregnant or suspected of having it. Human chorionic gonadotropin (hCG) is secreted by the chorion (the membrane of a fertilized egg). The main task of this hormone is to create in a pregnant woman’s body a hormonal background favorable for the formation and bearing of the fetus. The hormone also has an immunosuppressive effect on the body, i. somewhat reduces a woman’s immunity so that he does not reject the fetus as a foreign element.

Until the placenta is formed (this happens by 12-13 weeks), its protective function is performed by the corpus luteum. Outside of pregnancy, it usually self-destructs within two weeks of formation. If pregnancy occurs, the chorion begins to produce chorionic gonadotropin. This hormone does not allow the yellow theme to disappear. It continues to function for up to 10-12 weeks, producing the amount of progesterone and estrogen hormones necessary to maintain pregnancy. In the process of bearing a fetus, the entire body is rebuilt, which is a great stress for him. The hormone cortisol also secretes the corpus luteum and helps fight it.

HCG during early pregnancy has very little value. If the pregnancy proceeds normally, this one begins to grow rapidly, increasing every 2-3 days. This continues until the 11th week when the blood contains the maximum amount of the hormone. Having reached a peak, the concentration begins to decrease slowly. In case of deviations from the norm in any of the parties, it is necessary to consult a doctor. In this article, you will learn at what stage of pregnancy you can take an hCG test, why take it if you are not pregnant, and how to independently decipher the results, which may be indicated by too high or low levels of the hormone.

The Rabbit test, Friedman test

Have you ever heard of the “rabbit test”? In the early 20th century, to find out if a woman was pregnant, her urine was injected into a rabbit, after which an autopsy was performed and the animal’s ovaries were measured. If they increased, then the pregnancy was considered confirmed.

Important! The “pregnancy hormone” that the unfortunate rabbits were exposed to begins to be actively excreted in the urine of a pregnant woman a few days after conception.

In our time, fortunately, you can find out about its presence in the body without cruel experiments. A small strip of paper – a strip test for hCG – has become familiar to every woman.

What is HCG

HCG, or human chorionic gonadotropin, begins to be produced in a woman’s body in the first hours of pregnancy. It is produced by the embryo itself, or rather those of its cells, which will later become the placenta.

The main task of hCG at this time is to signal the corpus luteum, which remains in the place of the released egg in the ovary, that fertilization has taken place and to keep it from disintegrating at the end of the menstrual cycle.

Under the influence of hCG, the corpus luteum will remain active for 10-12 weeks, producing the progesterone necessary for the development and maintenance of pregnancy. Without progesterone, the lining of the uterus (endometrium) will collapse, pregnancy will end and menstruation will begin.

This is why hCG is needed to maintain a pregnancy in the first trimester until the placenta is mature enough to produce progesterone on its own.

Why determine hCG

Most often, hCG – more precisely, its beta subunit (β-hCG) – is determined in urine (qualitatively) or blood (quantitatively) to confirm or refute pregnancy.

Important! The most sensitive test strips for home determination of hCG in urine have a detection threshold of 10 mU/ml, corresponding to 10 days after conception. Determining hCG in the blood allows you to confirm pregnancy two days earlier – on day 8.

Types of hCG analyzes

Most often, hCG analysis is carried out to confirm and refute the fact of pregnancy. Blood is examined no earlier than 10 days after fertilization because. The hormone begins to be produced only when a fertilized egg attaches to the uterus, which most often occurs within a week. The hormone level in the blood reaches its maximum value at 10-11 weeks of pregnancy. The closer to childbirth, the lower its concentration. 7 days after birth, chorionic gonadotropin in the mother’s blood should not be detected or minimally present.

Human chorionic gonadotropin can also be secreted outside of gestation, for example, in diabetes, hormonal and endocrine disorders, some cancers, and the formation of benign tumors. Chorionic gonadotropin can be detected in the last two cases, even in men.

The hCG hormone consists of two units:

  • Alpha can also be released outside pregnancy, with endocrine or hormonal disorders.
  • Beta, which is unique and only released in pregnant women.

For an accurate diagnosis, patients may be prescribed different types of tests.

Total hCG

This type of analysis is often used to establish the fact of pregnancy in the first 2-3 weeks after conception. In the blood, the level of hCG rises much earlier and faster than in the urine. Therefore, a blood test can detect the onset of pregnancy much earlier than a test strip from a pharmacy or even a laboratory urine test.

Also, with the help of a general analysis, you can suspect multiple pregnancies. In this case, the level of hCG will be as many times higher as the fetus develops in the uterus.

In the second trimester, a general hCG analysis may be prescribed as part of perinatal screening. It is carried out simultaneously with the analysis of alpha-fetoprotein and estradiol.

Free hCG

This analysis reveals a tendency for the fetus to have Edwards or Down syndrome. It is prescribed in the second and third trimesters. Even with a positive analysis, it does not give a 100% guarantee that the child will have one of the syndromes, but it puts him at risk.

The presence of free b-hCG in the blood in men indicates the presence of testicular or trophoblastic formations (testicular cancer). If you suspect the presence of tumors, this study helps establish an accurate diagnosis and start treatment.

When to take an analysis

As mentioned earlier, hCG begins to be produced as soon as a fertilized egg attaches to the uterus wall and a protective shell (chorion) has formed around it. From this moment, the hormone level grows rapidly and after 2 days, it can be detected in the blood. But you should not go to donate blood for hCG on the very next day after intercourse. It is better to wait 10-11 days. There are two reasons for this:

  • Even if your body works like a clock, without additional diagnostics, you cannot know exactly when ovulation occurred. In addition, eggs live up to 2 days and sperm 5-7. Finding out exactly when their contact occurred is also almost impossible.
  • It takes time for a fertilized egg to leave the fallopian tube and enter the uterus. This may take 2 to 7 days.

Indications for the delivery of hCG

A blood test for chorionic gonadotropin can show the presence of pregnancy and its exact duration when the urine test (including pharmacy express tests) does not yet reflect the result and the fetal egg cannot be seen during an ultrasound examination. Also, this analysis is prescribed in case of contacting a gynecologist with complaints of a long delay in menstruation outside of pregnancy or abnormally heavy and prolonged uterine bleeding, which can provoke:

  • Severe stress.
  • Intoxication.
  • Infections.
  • Ovarian dysfunction.
  • The presence of a trophoblastic tumor.

In bearing a child, an analysis is prescribed for dynamic monitoring of the state of the fetus and the mother’s body. During perinatal diagnosis, hCG analysis is prescribed in the 2nd and 3rd trimesters.

Is it possible to determine the level of hCG at home?

You can use test strips at home. A reagent is applied to them, which reacts to a certain hormone concentration in the urine. If the hCG level exceeds the sensitivity, the strip changes color, which means pregnancy has occurred.

Since the level of chorionic gonadotropin in the urine rises more slowly than in the blood, it is possible to determine pregnancy with a high probability not earlier than the 5th day of delay.

level of hCG during pregnancy
level of hCG during pregnancy

In the first days after the start of the delay, only very sensitive express tests from 20-25 mU/ml or 10 mU/ml can show the presence of pregnancy. It is necessary to conduct a urine test with their help only in the morning when the concentration of hCG in the urine is the highest. Starting from the 5th week of pregnancy, the test can be performed any day due to increased hormone concentration.

The test strip may show a false positive result in some cases (when taking hormonal drugs or hormonal disruptions in the body).

Home pregnancy tests show only an increase in the hormone level but cannot measure its exact value. Only a laboratory blood test can determine the exact level of hCG during pregnancy.

During pregnancy planning, a woman can go to the laboratory and take an hCG test without a doctor’s prescription. She can state the presence of pregnancy and its approximate duration using a special table. Only an obstetrician-gynecologist can correctly interpret the results of a blood test for hCG, taking into account the results of other clinical studies.

The norm of hCG by weeks of pregnancy (decoding)

For healthy women who are not pregnant, an hCG level of 0-5 mU/ml is considered normal, and the result of a beta-hCG test should be negative.

During pregnancy, the normal concentration of chorionic gonadotropin directly depends on the period. The decoding of hCG by weeks of pregnancy is carried out using a special table.

Pregnancy TermThe indicator of hCG in the blood, / ml
no pregnancy0-5
2nd week25-300
3rd week1,500-3,000
4th week10,000—30,000
5th week31,000-151,000
6th week150 500-233 000
7-11 weeks200 800-291 000
11-17 weeks6 140-103 000
16-21 weeks4 720—80 100
21-39 weeks2 700—7 8100

Regardless of whether the pregnancy occurred naturally or after the IVF procedure, the same standard indicators are used in decoding.

To avoid confusion in the interpretation of the results, it is important to find out how your obstetrician-gynecologist calculates the gestational age, from when the last menstruation occurred to the moment of the alleged conception. Knowing the exact period, you can independently monitor whether the amount of the hormone is outside the normal range.

In some cases, at 34-39 weeks of gestation, there may be a slight jump in the concentration of hCG in the blood. Scientists believe this may be part of the preparatory phase before an early birth.

If the level of human chorionic gonadotropin is less than normal for a certain gestational age, this may indicate that a fertilized egg has attached itself outside the uterus. In this case, the hormone is produced in much smaller volumes.

Elevated hCG – what to do?

The level of human chorionic gonadotropin in pregnant women must be compared with the table above. If the result obtained exceeds the hCG norm by weeks of pregnancy, the cause may be the presence of such complications in the pregnant woman:

  • Multiple pregnancies.
  • early toxicosis or gestosis.
  • If the fetus weighs significantly more than normal.
  • The presence of diabetes.
  • Fetal chromosomal abnormalities.
  • Cystic drift.
  • Delayed pregnancy.

In women who do not bear a child, elevated hCG can be observed for the following reasons:

  • After taking hormonal drugs.
  • After a surgical abortion.
  • In the presence of neoplasms in the uterus, kidneys, lungs, and gastrointestinal tract.
  • With cystic drift or its recurrence.

For whatever reason, if an overestimated result of the level of hCG in the blood is obtained, you should immediately contact a gynecologist for further examination.

Low hCG – what to do?

A low value of human chorionic gonadotropin immediately after the onset of a delay in menstruation may indicate that pregnancy has not occurred or that its lines are still too small. If the study results indicate numbers from 5 to 25 mU/ml, then it is impossible to accurately say that pregnancy has not occurred. Perhaps the fertilized egg has just settled in the uterus, and hCG has just begun to be produced. In such cases, doctors prescribe a second blood test after 2-3 days.

If pregnancy is confirmed, hCG levels may decrease or increase too slowly for several reasons:

  • If a fertilized egg is fixed in the fallopian tube, ovary or abdominal cavity.
  • If the embryo has stopped its development (missed pregnancy).
  • With anomalies in the development of the fetus.
  • With the threat of spontaneous abortion (miscarriage).
  • With the true prolongation of pregnancy.
  • with placental insufficiency.
  • In case of fetal death in the 2nd or 3rd trimester.

A sharp decrease in the “pregnancy hormone” level in the later stages may indicate placental abruption.

Reasons for false test results

Possible reasons for a false negative result (when you are pregnant and testing does not show this):

  • The strip test is corrupted, or a lab error has occurred;
  • Urine is too diluted. You have drunk a lot of water, or there are physiological reasons for weakly concentrated urine;
  • Pregnancy is still too short. You rushed or incorrectly determined the time of ovulation;
  • Pregnancy is too long. After 5-8 weeks of pregnancy, hCG becomes too much, and this causes a malfunction of the strip test.

Possible reasons for a false positive result (when you are not pregnant and testing shows the presence of hCG):

  • the strip test is corrupted, or a lab error has occurred;
  • you evaluate the strip test significantly later than the recommended time;
  • You have recently had an HCG injection. When undergoing a fertility restoration program, hCG injections are used to induce ovulation, and one must wait at least two weeks before taking a pregnancy test;
  • you have recently experienced a pregnancy loss. Depending on the length of your pregnancy, hCG may take 2 to 8 weeks to return to pre-pregnancy levels.

How else can hCG produce itself?

HCG increases in the case of ectopic pregnancy in the same way as in the case of anatomically normal, but the rate of increase will be slower. However, it is impossible to determine an ectopic pregnancy only by the level of hCG. In case of violations during a normal, intrauterine pregnancy, the growth of hCG will also be slowed down.

In rare cases, hCG can appear in the body of a non-pregnant woman and even a man – in such cases, it indicates the presence of a tumor (both benign and malignant) that produces hCG.

hCG during pregnancy
hCG during pregnancy

Why determine hCG if pregnancy is already confirmed?

In early pregnancy, the trend of increasing hCG can serve as an indicator of the growth and development of the embryo. At the same time, any single analysis for hCG does not say much about the state of pregnancy or the fetus since the level of hCG varies greatly in different women.

Even in one woman, hCG levels can vary greatly from one pregnancy to another. More informative is the estimate of the doubling time of hCG in consecutive blood tests taken over several days.

During a normal pregnancy, the hCG value doubles approximately 48 hours before reaching a 1200-1500 mU/ml level and 48-72 hours after that. If the hCG level rises slowly or falls, this usually means a threatened abortion or an ectopic pregnancy.

However, after 5–6 weeks of pregnancy, an ultrasound will be a more accurate method of assessing the fetus’s condition. Your gynecologist will most likely order it for inconclusive hCG readings.

Despite the understandable desire of a woman to protect her unborn child, it is important to know that hCG cannot be safely increased on its own with the help of food or dietary supplements. Maintaining a healthy pregnancy depends on a delicate balance of hormones, which your doctor must monitor.


When should I donate blood for hCG?

For the test result to be reliable, blood must be taken on an empty stomach in the morning. Before blood sampling, it is advisable not to eat for 12 hours. If blood is donated during the day, it is impossible for 4 hours before the procedure.
In the morning, you should not take medicines that cannot be refused for medical reasons.
The day before the test, you can not engage in physical activity or sex, take alcohol, smoke, or eat spicy and fatty foods.
You can drink only clean water without gas in small quantities.
In emergency cases, for example, if a frozen (non-developing pregnancy) is suspected, the gynecologist may prescribe an urgent analysis for hCG. In this case, recommendations regarding food intake lose all meaning. The presence of hCG in the blood is important, not its exact amount.

How many days after conception can I take an analysis for hCG?

It is best to take an analysis for hCG after the start of the delay, after 3-5 days. Suppose additional studies were carried out in the process of pregnancy planning (an ovulation test was performed, a control ultrasound study), and you know exactly when ovulation and fertilization occurred. In that case, you can donate blood no earlier than ten days after that.
Suppose the study is carried out too early when the level of the body has not yet developed the hormone necessary to determine pregnancy. In that case, the result will be falsely negative, and the analysis will still need to be taken again after 3-5 days.

How accurate is a blood test for hCG?

Today, a clinical blood test is the most accurate method for measuring the concentration of hCG in the blood. The analysis may be unreliable due to laboratory error (which happens very rarely) or in such cases:
– When the patient is constantly taking medications that affect the hormonal background, if it is impossible to refuse to take them for medical reasons, it is necessary to warn the laboratory staff about this before taking the analysis. In this case, the result can be regarded as positive.
– Suppose ovulation or implantation of a fertilized egg occurred later than expected. In this case, a blood test will show too little hormone, that is, the absence of pregnancy. This happens when a sufficient amount of chorionic gonadotropin has yet to be developed. The analysis will have to be repeated to ensure that pregnancy has not occurred.

Is it necessary to donate blood for hCG for long periods?

In the second trimester, at a period of 15-16 weeks, pregnant women must undergo perinatal screening, including checking the level of hCG in the blood. It is highly desirable to conduct a study because it allows you to assess the risk of detecting serious developmental pathologies in a child (Down and Edwards syndromes, etc.), fetal growth retardation or spontaneous miscarriage.

This study is of particular importance for those categories of pregnant women who are at high risk of anomalies and retarded fetal development:
1. Women who became pregnant for the first time at age 35 and older.
2. Pregnant women in whose families there are people with developmental anomalies (Down syndrome, etc.).

A timely detected developmental anomaly allows for proper care and rehabilitation of the child immediately after birth. For high-risk pregnant women, doctors recommend giving birth in specialized perinatal centers, which have the equipment that may be needed to care for a special newborn.

Is it possible to take an analysis for hCG in different laboratories?

Different laboratories may use different research methods, different equipment and reagents. They can use other units to measure the hormone concentration (mg/ml or U / l) and standard indicators when interpreting the data obtained. By donating blood samples on the same day, in different laboratories, you can get a result that will be slightly, but still different.
To avoid receiving false results or incorrect interpretations, it is best to donate blood in the same laboratory every time.