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Chorionic gonadotropin B in pregnancy

Chorionic gonadotropin B is a hormone produced during pregnancy by the cells that form the placenta.

  • It is detected by a blood test about 11 days after conception.

  • It is detected by a urine test (pregnancy test) 12-14 days after conception.

  • B chorionic rapidly at the beginning of pregnancy and reaches its maximum value at 8-11 weeks of gestation. Then its value decreases continuously until the end of the pregnancy.

What you need to know about chorionic gonadotropin B

B chorionic values ​​during pregnancy should not be used to determine gestational age because they vary greatly,

  • In 85% of cases where the pregnancy progresses normally, the B chorionic will double every 48-72 hours.

  • The time it takes to double its value reaches 96 hours later in the first trimester of pregnancy.

  • The interpretation of B chorionic results requires special care. In a normal pregnancy with a good development there can be low values ​​of the hormone.

  • The urine test is a qualitative test and detects the presence of B chorionic in the urine. The result does not give an exact value.

  • The blood test is a quantitative test and measures exactly the value of the hormone and its changes.




How are the results of the B chorionic test interpreted?

Chorionic B is measured in mIU/ml values.


  • Values ​​below 5 are considered negative for pregnancy.

  • Values ​​above 25 are considered positive for pregnancy.

  • Values ​​from 6-24 are considered "grey zone". In these cases the measurement needs to be repeated to see if the value rises to confirm pregnancy.


Where do the B chorionic values ​​fluctuate during pregnancy?

B chorionic values ​​increase in early pregnancy. The range that varies depending on the week of pregnancy is quite large. Depending on the weeks that have passed since the last period (weeks of gestation) they are:

  • 3 weeks: 5-50

  • 4 weeks: 5-426

  • 5 weeks: 18-7340

  • 6 weeks: 1080-56500

  • 7-8 weeks: 7650-229000

  • 9-12 weeks: 25700-288000

  • 13-16 weeks: 13300-254000

  • 17-24 weeks: 4060-165000

  • 25-40 weeks: 3640-117000

The above values ​​of B chorionic gonadotropin are indicative. They change differently in each pregnancy. The way the hormone value changes is more important than its absolute value.


What do low B chorionic values ​​mean?

Low chorionic B values ​​may be normal or mask a problem. They should be repeated after 2-3 days (48-72 hours), preferably in the same laboratory, to see how they change

.

Low chorionic B can mean:

  • Incorrect calculation of gestational age (pregnancy being younger than we estimate).

  • Recurrent pregnancy or impending miscarriage.

  • Ectopic pregnancy.

What do high B chorionic values ​​mean?

High B chorionic values ​​can also be normal or hide a problem. They should be repeated after 2-3 days (48-72 hours), preferably in the same laboratory, to see how they change.


A high chorionic B value can mean:

  • Incorrect calculation of gestational age (the pregnancy should be older).

  • Multiple pregnancy.

  • Mule pregnancy.

Should I have repeat B choroid tests?

Repeat B choroid tests are usually done when there is a problem, such as:

  • If there is bleeding.

  • If you have severe abdominal pain.

  • If you have a history of miscarriage or ectopic pregnancy in a previous pregnancy.

  • Also if the hormone value was too low or too high in a previous test.

It is preferable to repeat the B chorionic examination:

  • To be done in the same laboratory. Different laboratories may use a different technique and this may affect the result and its correct interpretation.

  • To be done every two to three days, as this way we can calculate the expected rate of increase in the hormone, and compare it with the results we have, to see if they are normal.

How do B chorionic values ​​change after a miscarriage?

It can take up to 4-5 weeks after a miscarriage for B chorionic values ​​to return to the levels they normally have when there is no pregnancy (ie below 5).

The time period varies according to:

  • how the abortion took place (was it automatic or scraped) and

  • what was the B chorionic value when the miscarriage started.

B chorionic is more than halved every 2 days when there is complete miscarriage. We usually check with repeated measurements the reduction of the hormone until its value is below 5.

After a delivery it can take 4-6 weeks for the B choroid to become negative again.




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