hCG is also known as the “pregnancy hormone” and this is the hormone that detects your pregnancy (including your HPT) and maintains it. Let’s get to know more about it!
What is hCG?
Human chorionic gonadotropin or hCG is an important hormone during pregnancy. Post-implantation, the placenta secretes hCG. The hCG levels rise and then send a signal to the corpus luteum to release progesterone. This sustained release of progesterone maintains the uterine lining (prevents is shedding and getting your period) and maintains the developing embryo. This hCG signal/feedback is also referred to as “rescue of the corpus luteum.”
Is hCG present in your body when you are not pregnant as well?
Yes, in low quantities, i.e., < 5 IU/mL. These levels are too low to be detected in a home pregnancy test.
How does hCG level change after implantation?
This is known as a normal hCG rising pattern. Post-implantation the changes in the hCG levels are:
- hCG will double for every 48-72 hours.
- Then the hCG levels will then peak within the first 8-11 weeks of pregnancy
- The hCG will start dropping off from the peak
- The hCG level will reach a plateau and stay like that for the remainder of the pregnancy
Note: The value of hCG levels isn’t as important as the doubling pattern of hCG levels every 48-72 hours. In a high-risk pregnancy or in recurrent miscarriages, a serial beta hCG test is done to see how fast hCG is being produced.
What level of hCG is considered to be positive for pregnancy?
Post-implantation, as the pregnancy progresses, the hCG levels rise and becomes > 25 IU/mL, the woman is then considered pregnant.
An HPT (home pregnancy test) will test the presence or absence of hCG in your urine (quantitative test) not the amount of hCG present (qualitative test) and you will need at least 2- 3 weeks post-conception (some tests, like blood tests, are more sensitive can detect earlier). It would be best to test it after your missed period to prevent a false positive.
Some tests get a positive earlier than 2 weeks as they detect a variation of hCG, i.e., hyperglycosylated hCG (H-hCG). hCG (regular) is produced post-implantation whereas H-hCG is released earlier, sometime after fertilization. Hence, the H-hCG levels are typically higher than hCG levels.