hCG, commonly called human chorionic gonadotropin, is a hormone that your placenta produces once you conceive. Doctors also call it the "pregnancy hormone" because it helps nourish the egg.
When people think about this hormone, they often want to know how much should hCG increase. Typically, your hCG levels should increase within 48 hours of implantation and double up every 48 hours to 72 hours in the first 8–11 weeks of pregnancy.1 So, you can see a change in hCG levels within two days after the egg attaches itself to the uterus.
However, the changes in hCG levels are not uniform throughout your pregnancy. There might be episodes when hCG stops doubling, and there might be two reasons for this. First, your hCG levels might not double as rapidly as in the first four weeks of pregnancy. Secondly, your hCG levels might also stop doubting if your foetus has some serious underlying issue or you've suffered a miscarriage.
How Does hCG Work in Pregnancy?
Syncytiotrophoblastic cells present in the placenta yield hCG. It triggers the corpus luteum2 to produce progesterone. This hormone helps maintain and cater to the growth of your foetus. It also thickens the walls of your uterus, supporting embryonic growth by ensuring the continued supply of maternal hormones and nutrients, stopping menstruation. Are you wondering when does hCG stops doubling or how much it rises in 2 days?
Typically, hCG production is the highest during the first 8–10 weeks of your pregnancy and doubles every 48 hours until it reaches 1,200 mIU/mL.
And it's very natural to think, what if hCG levels don't double in 48 hours? Once the level reaches 1200 mIU/L, beta hCG doubling time can reduce slightly and take approximately 3.5 days. The doubling time for hCG can also take approximately four days when the hCG levels rise and reach 6000 mIU/L in the later stages of the first trimester.
Finally, you can expect hCG levels to stop rising around the 11th week of your pregnancy, and this phase generally marks the hCG peak.
Understanding Doubling hCG Level
You must know how much hCG increases daily and when and how fast the hCG levels rise.
Having a clearer picture of your beta hCG doubling time and knowing when hCG stops doubling can help you monitor your pregnancy better. Furthermore, it can also help reduce concerns and myths related to pregnancy and miscarriage. Here are some of the facts that you must know:
What is hCG Doubling Time?
hCG starts doubling after you conceive. Typically, hCG levels should increase in 48 hours, especially in the first four weeks of pregnancy. This phenomenon is called hCG doubling time. The doubling time for hCG can increase in the advanced stages of pregnancy. So, it won't double up in 2 days but within 3 or 4 days, depending on the previous hCG levels.
When Does hCG Start Doubling?
After you conceive, the doubling time for hCG is ideally 48 hours in the first four weeks of pregnancy.
How Often Should hCG Levels Double?
hCG should increase every 48 hours in the first 8–10 weeks of pregnancy. Once it reaches a certain level, that is, 1200 mIU/L, the frequency of hCG doubling reduces, and instead of 2 days, you might witness a rise in hCG after every 3.5 days.
Furthermore, in the final trimester, especially after the 24th week, hCG production reduces and beta hCG doubling stalls. Overall, your hCG levels double up every four days until they reach 12,000 mIU/L.
What Factors Can Affect hCG Doubling Time?
Is your hCG rising but not doubling? While that might seem concerning, several factors can cause this. The condition of your foetus, its growth, and your trimester determine the hCG doubling time.
For instance, beta hCG doubling can occur every 48 hours in the first trimester and reduce gradually. Hence, knowing how often hCG doubles makes detecting any condition in your embryo straightforward if your hCG doubling time doesn't align with the clinically approved hCG levels.
hCG Doubling Time Expectations
The placenta produces the human chorionic gonadotropin (hCG) hormone during pregnancy. Its levels rise rapidly in the early stages of pregnancy.3 The hormone plays a crucial role in supporting the development of the foetus. Therefore, monitoring hCG levels and their doubling time can provide valuable insights into the progression of pregnancy and the foetus viability.
Let's take a look at a detailed explanation of hCG levels doubling up over the weeks of pregnancy and the expected hCG doubling time for each stage to get a clearer insight into the matter:
Early Pregnancy (Before 6 Weeks)
Let's start with the most important part: When do hCG levels rise or double?
Doubling hCG levels is seen during the early stages of pregnancy, specifically before six weeks as the placenta develops. The doubling time of hCG during this period is approximately every 48 to 72 hours, and this quick rise in hCG is a crucial sign of a normal and healthy pregnancy.
However, it's important to note that individual hCG levels can vary widely, and there is a range of usual doubling times. Because of this, repeated measurements over time help to accurately check the health of the pregnancy. In this phase, hCG levels can vary from 5 to 117,000 mIU/mL, depending on your pregnancy week.4
First Trimester (6-12 Weeks)
hCG levels rise in the first trimester of pregnancy, from 6 to 12 weeks. However, it happens at a slower pace compared to the early stages.
How often does hCG double? The doubling time of hCG extends slightly during this period, occurring approximately every 72 to 96 hours. This steady increase shows that the placenta is developing and the mother-baby blood flow is being established. Although changes in the expected doubling time can be worrying, it's vital to understand that differences between individuals can happen. Regular prenatal care is crucial to keeping an eye on the health of both the mother and the baby.
While hCG levels can be 1080 mIU/L in the 6th week, they can increase to 288,000 mIU/mL in the 12th week of pregnancy.
Second Trimester (13-26 Weeks)
As pregnancy progresses into the second trimester, from 13 to 26 weeks, hCG levels plateau and eventually decline. During this time, the doubling time of hCG gets longer, happening about every 96 to 120 hours.
This decrease in the rate of hCG rise is a normal part of pregnancy progression and is indicative of the maturation and stabilisation of the placenta. While variations in hCG levels and doubling time can occur among individuals, regular prenatal monitoring remains essential to ensure the health and development of both the mother and the baby. While your hCG levels can reach 13,300 mIU/L in your 13th week of pregnancy, they can increase to 165,400 mIU/mL in the 26th or even more.
Third Trimester (27- 40 Weeks)
If your hCG is rising but not doubling during the third trimester of pregnancy, spanning from 27 to 40 weeks of gestation, there's nothing to be worried about. The doubling time of hCG further extends during this late stage of pregnancy, occurring approximately every 120 to 144 hours. This gradual decrease in hCG levels reflects the ongoing maturation of the placenta and the transition towards the final stages of pregnancy. hCG levels may go as high as 117,000 mIU/mL in your final trimester and then start decreasing.
While hCG levels reach their lowest point by the time of childbirth, variations in levels and doubling time can still occur. Regular prenatal care and monitoring help ensure a safe and healthy delivery for the mother and the baby.
hCG Levels Not Doubling
What if hCG levels don't double in 48 hours? While hCG doubling up may vary due to many reasons, there are significant chances that your pregnancy might have complications. Here are some reasons why your hCG isn't doubling up.
Possible Reasons for hCG Not Doubling:
Now that you know when hCG stops doubling and how much hCG should increase in the different stages of your pregnancy, here are some possible reasons why your hCG might not double as usual. You must also remember that it's not enough if your hCG is rising but not doubling in the initial weeks of the pregnancy.
- Ectopic Pregnancy: In some cases, hCG levels may not double due to an ectopic pregnancy, where the fertilised egg implants outside the uterus, most commonly in the fallopian tube. This situation is a medical emergency requiring immediate attention. Ectopic pregnancies can be life-threatening as the fallopian tubes can burst, leading to excessive bleeding in mothers. It finally leads to miscarriage.
- Miscarriage: A non-doubling trend in hCG levels could indicate a potential miscarriage or pregnancy loss. When you have a miscarriage, your hCG levels start decreasing until they reach the baseline in a few weeks. Such a condition also needs immediate medical evaluation and treatment in complicated cases of excessive bleeding. However, there's no need to check your hCG levels once you lose your pregnancy, as the body will automatically balance them.
- Gestational Age Miscalculation: An incorrect estimation of gestational age can lead to a misinterpretation of hCG level expectations, causing unnecessary concern. Hence, it is always crucial to get a beta-hCG pregnancy test followed by an ultrasound to determine the exact age of the foetus. The age of your foetus or the week of pregnancy determines the hCG levels and their production. Thus, it is crucial to get an accurate calculation of the same.
- Slow Embryo Development: Impaired embryo development can result in slower-than-expected hCG level increases, requiring close monitoring to assess pregnancy viability. If your hCG is not doubling but increasing, it might indicate stunted embryonic growth. It is because hCG helps nourish and grow the embryo, and reduced growth in hCG levels can indicate a malnourished foetus.5
When to Be Concerned:
- Stalled or Declining hCG Levels: Plateauing or decreasing hCG levels over multiple tests are red flags, signalling a potential problem with the pregnancy.
- Symptoms of Ectopic Pregnancy: Pain, vaginal bleeding, and other ectopic pregnancy symptoms demand immediate medical evaluation to prevent serious complications.
- Persistent Low hCG Levels: Consistently low hCG levels may indicate an unhealthy or non-viable pregnancy, necessitating further investigation and medical management.
What to Do If Your hCG Levels Are Not Doubling:
Consult Your Healthcare Provider: Any irregularities in hCG levels or concerning symptoms should prompt immediate contact with a healthcare provider for evaluation and guidance.
- Further Testing: Doctors may recommend tests, such as ultrasound, to assess the pregnancy's health and determine the cause of hCG level discrepancies. Further, you may also have to undergo other blood tests for pregnants.6
- Regular Monitoring: Continuous monitoring of hCG levels may be necessary to track pregnancy progression and facilitate timely intervention if needed.
How can hCG Testing Assist You, and How Often Should It Take Priority?
- Early Pregnancy Detection: hCG testing helps confirm pregnancy in its early stages, often before a missed period, enabling prompt prenatal care initiation.
- Monitoring Pregnancy Progression: Serial hCG testing allows healthcare providers to monitor pregnancy progression and detect abnormalities early, guiding appropriate management decisions.
- Frequency of Testing: While standard practice involves hCG testing at the initial confirmation of pregnancy, women with a history of fertility issues, miscarriages, or high-risk pregnancies may require more frequent testing to ensure close monitoring and timely intervention if complications arise.
Conclusion
Understanding hCG levels and their significance in pregnancy is essential for ensuring the mother's well-being and monitoring foetal growth. While beta hCG doubling indicates foetal growth, any deviation can indicate issues in your pregnancy, which can lead to miscarriage. However, prompt medical assessment and management can help address underlying issues. Overall, hCG testing and regular evaluation can help you rule out any condition in your embryo or even terminate your pregnancy if it has serious conditions.
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