Human Chorionic Gonadotropin, the famous HCG. The pregnancy hormone!!! When fertilization occurs, the zygote slowly travels to the uterus, and if the endometrium (the well-known layer that sheds during menstruation) is in good condition in terms of thickness and texture, it implants and truly initiates pregnancy.
Responsibility of HCG
HCG is one of the most responsible and important hormones in pregnancy. It prevents the corpus luteum from being destroyed, which ensures that the endometrium is not shed. The corpus luteum secretes progesterone. In that ovary, the egg matured and was later released, then traveled to the fallopian tubes, where it was fertilized by the sperm. This hormone is exclusive to pregnancy and rises very rapidly at the beginning, as this is when it is most essential. Through it, pregnancy can be detected as well as the approximate gestational age1.
Pharmacy pregnancy tests have a reagent that makes the positive line appear when there is HCG in a woman’s urine. Laboratory tests serve the same function and are very similar in method. The biomedical scientist simply switches urine for blood plasma and, if positive, can measure the amount of HCG in the plasma sample2.
If the test result only says REACTIVE, the test was done like a urine test, without measuring hormone levels. This is a qualitative HCG test. But if it looks like the one in the photo below, with a hormone count, then it’s a quantitative test (which measures hormone levels).
So when should I consider the HCG hormone test positive?
This is an example of a laboratory quantitative HCG test with a result of 307.2 mIU/ml. Anything above 25 mIU/ml is already considered positive. So I was actually pregnant! And pregnant for approximately 3 weeks, according to a chart used to compare HCG levels.
My pregnancy test from my last pregnancy
The tables exist to help, but they can sometimes be confusing, since a woman may have ovulated later than her period would suggest. For example: a typical cycle is about 28 days, and you count 14 days from the first day of menstruation, so 28 – 14 = 14.
Menstruation would happen around day 14 of the cycle, but in my case, my cycle was 31 to 33 days, so I considered that menstruation could occur around the 15th to 17th day, causing a difference that really does matter at this stage.
Chorionic Gonadotropin – Beta HCG – Weeks and Values (mIU/mL)
| 1 week | 5 to 50 mIU/mL |
| 1 to 2 weeks | 50 to 100 mIU/mL |
| 2 to 3 weeks | 100 to 5000 mIU/mL |
| 3 to 4 weeks | 500 to 10,000 mIU/mL |
| 4 to 5 weeks | 1000 to 50,000 mIU/mL |
| 5 to 6 weeks | 10,000 to 100,000 mIU/mL |
| 6 to 8 weeks | 15,000 to 200,000 mIU/mL |
| 2 to 3 months | 10,000 to 100,000 mIU/mL |
There are many charts, but this one worked best for me in two pregnancies. There are also cases where HCG appears outside of pregnancy, but this is very rare. Some types of tumors can secrete HCG, but in such small quantities that a pregnancy test would not pick it up.
Indeterminate test
My test results came back indeterminate several times until it finally turned positive. Could I be half-pregnant? No, that’s not the case—and it’s not even that uncommon. The problem is that some labs have a rather high threshold for marking a test as positive, so the result may fall into a gray area that neither confirms nor rules out pregnancy.
It is recommended to repeat the test after 48 hours, because in that period the value is expected to nearly double. However, in some cases the level may not double or may even drop. In that case, you should see your doctor. You may have had fertilization and the start of implantation, resulting in a chemical pregnancy3.
Important tip: A good pregnancy test is one with very high sensitivity, meaning it detects even very small amounts of HCG in the urine. A highly sensitive test is Famivita. It has 10 mIU sensitivity, compared to the 25mIU tests available on the market. The Famivita test can detect pregnancy up to 5 days before your missed period, if HCG is present. You can find pregnancy tests here.
See also: Pregnancy Test – Beta HCG Quantitative and Qualitative, What’s the Difference?
