What is hCG Human Chorionic Gonadotropin?
Human chorionic gonadotropin (hCG) is the pregnancy hormone which is produced by the placenta soon after implantation. Implantation takes places around six to twelve days after ovulation or about five days before a missed period. After the implantation, the hormone enters the blood stream. It shows up in the blood within two to three days and in urine within three to four days of implantation. The pregnancy blood or a pregnancy serum test detects the exact amount of the hormone in the blood. The test shows positive during a missed period (1).
Increase Of hCG In Early Pregnancy:
Once the fertilized egg attaches to the uterine wall, the hCG levels rise rapidly. The levels increase throughout the first trimester and reach a peak at around 60 to 80 days after fertilization (2). Now is when you experience early pregnancy symptoms such as sore breasts, irregular spotting, vomiting, or pelvic pain, for which you should go for a pregnancy blood test for confirmation.
Normal hCG Doubling Time And How Often Does hCG Double?
hCG doubles every 48 to 72 hours in early pregnancy, and there will be no normal hCG value in the first trimester. On an average, the levels double every 30.9 hours until they reach 6500 mlU/ml in the eighth week of the last menstrual period (LMP). After this, the levels increase considerably and peak between the ninth and twelfth week. The hCG levels then decrease slightly from the 12th to 16th week, after which the levels remain constant until the end of pregnancy.
| hCG Level | Doubling Time Expected |
|---|
| Below 1,200 mlU/ml | 48–72 hours |
| 1,200 – 6,000 mlU/ml | 72–96 hours |
| Above 6,000 mlU/ml | Over 96 hours |
More on early hCG levels
- A 48-hour increase in hCG levels by minimum 63% is considered normal.
- If the levels are above 6000 mlU/ml, it takes around four or more days for the value to double.
- When the hCG values reach up to 7200 mlU/ml, you can see a yolk sac.
- When the levels are greater than 10800 mlU/ml, you can see a visible embryo with a heartbeat.
Normal Pregnancy hCG Values
Below is the normal amount of serum hCG levels by weeks calculated from LMP
| Pregnancy Week | Normal Hcg Levels |
|---|
| 3 weeks | 5–50 mlU/ml |
| 4 weeks | 4-426 mIU/ ml |
| 5 weeks | 19-7,340 mlU/ml |
| 6 weeks | 1,080-56,500 mlU/ml |
| 7-8 weeks | 7,650-229,000 mIU/ml |
| 9-12 weeks | 25,700-288,000 mIU/ml |
| 13-16 weeks | 13,300–254,000 mIU/ml |
| 17-24 weeks | 4,060-165,400 mIU/ml |
| 25-40 weeks | 3,640-117,000 mIU/ ml |
- below five mlU/ml for women pregnant who are not.
- The normal hcg levels for postmenopausal women go up tp 14 mlU/ml.
- If the hCG levels are between 5 and 25 mlU/ml, it is considered “equivocal”. It means you may or may not be pregnant and you would have to repeat the test.
- If hCG levels are above 25 mlU/ml, you are pregnant.
What Is hCG Pregnancy Test?
The hCG pregnancy test helps you determine whether or not you are pregnant. If your blood shows hCG, then you are pregnant. With the progressing pregnancy, the hCG levels will fluctuate a lot and there will be several normal levels.
Dropping and Slow Rise hCG Levels
Dropping hCG levels indicate that pregnancy is not viable. It is usually associated with failed pregnancies such as chemical pregnancies or miscarriages. Slow rise hCG levels are linked to miscarriages or ectopic pregnancies (3). A decline in hCG levels that is slower than 21% to 35% in 48 hours is abnormal and is associated with ectopic pregnancies or the presence of trophoblastic tissue (4). Also, if the hCG levels are above 6000 mlU/ml, it is not easy to detect the possibility of pregnancy. Here, a sonogram is the best option to know the pregnancy status.
What Is An hCG Level Calculator?
hCG calculator is a tool for detecting whether or not you are pregnant and if the pregnancy is progressing normally. You can use it to calculate the hCG doubling time by using two consecutive hCG levels, the number of days past ovulation, and the time between the tests. Once you provide these values, hCG levels calculator will automatically calculate the results. It creates an hCG levels chart which allows you to monitor the increase associated with the low, average, and high hCG levels.
hCG Levels In Twin Pregnancy
A twin pregnancy cannot be detected from hCG values. The hCG levels rise faster in case of twins, but there isn't much scientific data on this. However, more than one fetus could have various reasons.
Beta hCG Levels And Their Interpretation
- It is a quantitative hCG test that measures the amount of hCG hormone in the blood and can detect pregnancy at a much earlier stage, i.e., as early as two to three days following implantation, or eight to nine days following fertilization.
- Urine hCG levels are lower than blood hCG levels, and thereby blood hCG test is more sensitive and reliable. It also helps in managing pregnancy problems.
- Beta hCG levels double every two days in the first four weeks of pregnancy.
- Blood hCG tests are not helpful to understand the viability of pregnancy if the levels are over 6,000 mlU/ml, or after you are six to seven weeks into pregnancy. In such cases, an ultrasound is more helpful.
- Beta hCG doubling calculator can be used to calculate the doubling time of two beta hCG samples by entering the date of the blood test and the corresponding beta hCG value for that day
Some Facts About HCG
- hCG test is useful in assessing pregnancy before the fetal heart rate is detected (that is before six to seven weeks into pregnancy). It helps in ruling out an early miscarriage or ectopic pregnancy.
- The hCG level increases slowly above 6,000 mlU/ml, and these levels say nothing about the progression of pregnancy. After two to three months, hCG levels slow down further, and then plateau before delivery.
Disclaimer: One of your first brushes with hCG will be when you take a home pregnancy test or get a blood test done to determine whether or not you are pregnant. Whatever your results, make sure you run them by your doctor to know exactly what's happening. It's possible that the hCG levels may sometimes also show a false reading, it is best to get it checked through your medical care professional.
Moms, did you take a urine test or blood test to check your pregnancy status? Did the results come out accurate or were you confused?
References:
[1] T Chard; Pregnancy tests: a review; Human reproduction (1992). https://pubmed.ncbi.nlm.nih.gov/1639991/
[2] Gerald Konrad; First-trimester bleeding with falling HCG; Canada Family Physician (2007). https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1949168/
[3] Pregnancy test. https://medlineplus.gov/ency/article/003432.htm
[4] W Y Zhang and G L Yen; Serum SP1, hPL and beta-hCG levels in trophoblastic diseases; Chinese Medical Journal (Engl) (1991). https://pubmed.ncbi.nlm.nih.gov/1723674/
