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hCGPregnancy

hCG

August 3, 2021

Pregnancy

What is hCG?

Human chorionic gonadotropin (hCG) is a hormone produced by trophoblast cells surrounding the embryo. These cells later form the placenta, the organ that provides the growing baby with nutrients.

hCG is produced about 6 days after fertilisation and can often detectable in the blood about 11 days after conception. It is recommended to take this test from the first day of the missed menstrual period at the earliest.

In early pregnancy, hCG levels typically double every 48-72 hours, the longer into the pregnancy the slower hCG levels double. The peak is reached around 8-11 weeks of pregnancy.

In short, it is useful to analyse hCG levels in the blood to:

  • Detect pregnancy

  • Detect potential miscarriage

  • Detect potential abnormal pregnancies such as molar pregnancies

  • Detect certain tumours

Why is this analysis important?

Over-the-counter pregnancy stick tests measure hCG in the urine to tell you if you are pregnant or not. However, these tests cannot tell you the exact concentration of hCG. Quantitatively measuring the amount of hCG in the blood can give you more information about your pregnancy, such as if your hCG level is higher or lower than the expected value for your gestational age.

Higher hCG values than expected for the gestational age can be associated with multiple pregnancies or abnormal pregnancies such as a molar pregnancy and lower hCG values than expected can be associated with non-viable or ectopic pregnancies. Following hCG values over time can help detect potential miscarriages.

hCG is also a tumour marker. High hCG levels in non-pregnant women or men can be associated with certain tumours such as lung cancer, testicular cancer, breast cancer etc.

Results

The reference range for hCG levels in the blood can be different depending on the laboratory and technique used. It is important to take into account the gestational age when evaluating hCG levels.

High hCG levels in the blood often confirms pregnancy, but can also be signs of certain tumours. Low hCG levels are normal in non-pregnant women and men. Lower hCG level than expected for the gestational age can be a potential sign of miscarriage.

Other Considerations

hCG value can sometimes fall within a “grey zone”, which means that it is neither possible to rule out or confirm pregnancy. In these cases, a repeat test will be needed after at least 5 days.

Monitoring hCG levels during early pregnancy can help track the progression of pregnancy, but the results will always need to be confirmed by an ultrasound examination. hCG levels cannot determine the location of the pregnancy, i.e. whether the egg has implanted within the womb or outside, and cannot determine the number of fetuses, i.e. whether it is a singleton or multiple pregnancy.

Tests that include this marker

References

https://www.healthline.com/health/hcg-blood-test-quantitative#whats-hcg

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