Human chorionic gonadotropin (hCG) is the pregnancy hormone. This hormone ensures that the corpus luteum (ovarian follicle after ovulation) maintains progesterone production after conception has occurred.
HCG is produced by the embryo. For this reason, pregnancy tests are based on detecting hCG in blood or urine, since its presence is indicative of pregnancy. Specifically, pregnancy tests detect the beta subunit of this hormone, which is why they are also known as beta hCG tests.
However, hCG hormone levels decrease to be undetectable in case of miscarriage.
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hCG during pregnancy
The hCG hormone can be detected in the urine more reliably once the missed or delayed period has occurred. At this point, hCG levels are sufficiently elevated for the test to detect them.
On the other hand, blood tests are usually more sensitive and are able to detect lower amounts of hormone and, more importantly, to quantify it and provide a value.
Generally, hCG values double every 48-72 hours during the first 12 weeks of gestation. From this point on, hCG levels will gradually decrease. For this reason, normal hCG values vary according to the gestational period in which the woman is.
Thus, and especially in the case of low or doubtful values, it is of great importance to repeat the test serially with a minimum interval of 48 hours to verify that the increase in hCG is produced and to follow up. If there is an increase in beta hCG hormone levels, the specialist will schedule the ultrasound at 6-7 weeks of gestation. O
n the other hand, when hCG levels do not match what is expected or do not increase at the rate they should, it is time to think about the possibility that something is going on. Failure to double these hormone levels can be a poor prognostic sign and usually indicates problems in the gestational progression.
Miscarriage and beta hCG levels
A miscarriage is the loss of a pregnancy before the 20th week of gestation and can be due to different factors. One of them is chromosomal abnormalities in the embryo, although it is not the only one. However, the cause of gestational loss is not known in most cases.
When a miscarriage occurs, beta hCG levels decrease, although it takes about 3-6 weeks for the body to make it undetectable. Therefore, the woman may continue to have hCG hormone in her blood for some time after the miscarriage has been confirmed, but these levels will decrease.
If hCG hormone values do not decrease after a miscarriage, it may mean that embryonic tissue still remains in the woman. In this case, a specialist will assess whether you need some kind of intervention.
FAQs from users
What does a positive beta, but low hCG levels mean? Am I going to have an abortion?
HCG is a hormone that is produced specifically in the trophoblast (the structure that will later give rise to the placenta) and that maintains the corpus luteum so that it continues to produce hormones that, in turn, will maintain gestation. It is made up of two subunits, the alpha subunit which is common to other hormones produced by the pituitary gland and the beta subunit which is specific to HCG.
As gestation progresses, the levels of this hormone increase. Although there are large variations from one week to the next, and even from one day to the next, there are approximate values for each period of pregnancy. Therefore, in early pregnancy, a low Beta HCG may be indicative of a pregnancy that is not progressing properly.
However, as mentioned above, given the high variability in the concentrations of this hormone and its daily changes, the determination of a single value is not predictive of the evolution of the pregnancy. If there are doubts as to the normality of its values, we usually determine it serially (approximately every 48 hours) to see if the HCG levels increase adequately.
Is it necessary to wait some time after a miscarriage for a new embryo transfer?
A miscarriage has a physical and physiological impact on women. In addition, it is often accompanied by a psychological impact. Therefore, it is important to assess each situation prior to performing a new embryo transfer.
Do I need a curettage if hCG levels do not decrease after an abortion?
The specialist will always be the one to assess the situation. It is true that the gynecologist may choose to perform a uterine curettage to eliminate the embryonic remains that cause the hCG not to decrease after the abortion, if they are not expelled naturally.
Is it possible for me to have a positive pregnancy test if the gynecologist has told me that I have had an abortion?
Yes, after the abortion, hCG levels will decrease until they become undetectable. This will take about 3-6 weeks. For this reason, if you take a pregnancy test during this period, you may still test positive even though you have miscarried.
However, it is important that the hCG values after the miscarriage are decreasing. Otherwise, it is possible that there is still embryonic tissue inside your body and the specialist will have to assess whether you need some kind of treatment.
Suggested for you
If you want to continue reading more in depth about hCG levels in pregnancy, you can visit the following link: What are the normal values of beta-hCG hormone?
If, on the other hand, you need more information about miscarriage, we recommend you read the following article: Miscarriage: symptoms, causes and consequences.
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FAQs from users: 'What does a positive beta, but low hCG levels mean? Am I going to have an abortion?', 'Is it necessary to wait some time after a miscarriage for a new embryo transfer?', 'Do I need a curettage if hCG levels do not decrease after an abortion?' and 'Is it possible for me to have a positive pregnancy test if the gynecologist has told me that I have had an abortion?'.