Human chorionic gonadotrophin (hCG) is a hormone produced during pregnancy. After you conceive (when the sperm fertilizes the egg), the developing placenta begins to produce and release hCG. It is made by cells formed in the placenta, which nourishes the egg after it has been fertilized and has attached itself to the uterine wall.

If you are pregnant, you can detect it in your urine. This is what happens when pregnant women do a pregnancy test at home. In case of a pregnancy test at home with a pregnancy test, with the help of that pregnancy test kit, actually, test for the presence of Human Chorionic Gonadotrophin (hCG) happens.

If hCG is present, then the pregnancy test will be positive, and that means you are pregnant unless there is a false positive pregnancy test.

Blood tests measuring hCG levels can also be used to check how well your pregnancy is progressing, including your baby’s development. Though some medical practitioners don’t recommend using the blood hCG levels to calculate the date of a pregnancy since these numbers can vary so widely.

Human Chorionic Gonadotrophin (hCG) levels can first be detected by a blood test about 11days after conception and about 12-14 days after conception by a urine test. Low levels of hCG may be detected in your blood within about 7 days of you becoming pregnant.

hCG levels are highest towards the end of the first trimester, then gradually decline over the rest of your pregnancy.

Typically, the hCG levels will double every 3 days (72 hours). The level will reach its peak in the first 8-11 weeks of the pregnancy. After this point, the hCG level will gradually decline and level off for the remainder of the pregnancy.

Key Things to Remember About HCG Levels

For hCG levels to be high enough to be detected in your urine using a home pregnancy test, it takes about 2 weeks.

In most (around 85 percent)  normal pregnancies, the hCG level will double every 2 to 3 days (48 – 72 hours).

As you get further along in pregnancy and your hCG level gets higher, the time it takes to double can increase to about ( 96 hours.).

hCG is made by the placental cell, and the placenta is responsible to transport nourishment from you to the baby in your womb.  Therefore low hCG levels can indicate a placental defect, meaning your baby may not be able to get the nourishment it needs from you. The hCG hormone is measured in milli-international units per milliliter (mIU/mL).

An hCG level of less than 5 mIU/mL is considered negative for pregnancy, and anything above 25 mIU/mL is considered positive for pregnancy.

An hCG level between 6 and 24 mIU/mL is considered a grey area, and you’ll likely need to be retested to see if your levels rise to confirm a pregnancy. But you should not be too concerned about your hCG numbers. A normal pregnancy can have low hCG levels and result in a perfectly healthy baby. The results from the ultrasound exam done around 5 -6 weeks gestation, give a better picture of the health of your baby than your hCG levels.

One of the first signs of pregnancy to show up on ultrasound is the gestational sac, the sac which encloses the developing baby and contains amniotic fluid. The gestational sac is found in the uterus and on an ultrasound, it appears as a white rim around a clear center.

 

 

The gestational sac forms around five to seven weeks after the last menstrual period in natural cycles. Thus, it is usually visible between three and five weeks gestational age using a transvaginal ultrasound.

A transvaginal ultrasound has a higher sensitivity and produces clearer images than a transabdominal ultrasound. A transvaginal ultrasound should be able to show at least one gestational sacs once the hCG levels have reached between 1,000 – 2,000 mIU/mL. Because levels can differentiate so much and conception dating can be wrong, a confirmed diagnosis should not be made by ultrasound findings until the hCG level has reached at least 2,000 mIU/mL. The hCG levels should not be used to date a pregnancy since these numbers can vary widely from person to person.

A single hCG reading is also not enough information for most diagnoses. When there is a question regarding the health of the pregnancy, multiple tests of human Chorionic Gonadotrophin (hCG) levels are done a couple of days apart to give a more accurate assessment of the situation.

There are two common types of hCG tests. A qualitative hCG test detects if hCG is present in the blood. The other type, a quantitative hCG test (or beta hCG) measures the amount of hCG actually present in the blood.

Average Human Chorionic Gonadotrophin (hCG) levels during pregnancy

The average hCG levels in a pregnant woman’s blood, in weeks from Last Menstrual Period (gestational age)*, are:

  • Borderline pregnancy result – 10 to 25 U/L
  • Positive pregnancy test – more than 25 U/L
  • Pregnant women 3 weeks after LMP: 5 – 50 mIU/mL
  • Pregnant women 4 weeks after LMP: 5 – 750 mIU/mL
  • 5 weeks LMP: 200– 7,340 mIU/mL
  • 6 weeks LMP: 1,080 – 56,500 mIU/mL
  • 7 – 8 weeks LMP: 7, 650 – 229,000 mIU/mL
  • 9 – 12 weeks LMP: 25,700 – 288,000 mIU/mL
  • 13 – 16 weeks LMP: 13,300 – 254,000 mIU/mL
  • 17 – 24 weeks LMP: 4,060 – 165,400 mIU/mL
  • 25 – 40 weeks LMP: 3,640 – 117,000 mIU/mL
  • Postmenopausal females: 0 – 8 mIU/mL

* These numbers are just a guideline. Every woman’s level of hCG can rise differently. The actual levels are of less significance than the rise in hCG levels during the course of the pregnancy.

The amount of hCG in your blood can give some information about your pregnancy and the health of your baby.

I have a low HCG level, what does it mean?

A low Human Chorionic Gonadotrophin (hCG) level can mean any number of things. They should be rechecked within 48-72 hours to see how the level is changing. A low hCG level can indicate:

  • Miscalculation of pregnancy dating
  • Risk of a miscarriage blighted ovum.
  • A loss of pregnancy (miscarriage).
  • Ectopic pregnancy– where the fertilized egg implants in the fallopian tube.
  • Problems with the growth or development of the baby

I have a high HCG Level in my test. What does it mean?

A high level of hCG can also mean a number of things. This should also be rechecked within 48-72 hours to evaluate changes in the level. A high hCG level can indicate:

  • Miscalculation of pregnancy dating
  • Molar pregnancy
  • Multiple pregnancies (for example, twins or triplets)
    • Human Chorionic Gonadotrophin (hCG) levels are usually much higher when there is more than one fetus.
  • If you are not pregnant, then abnormal tissue growth in the ovaries or uterus, consult your doctor immediately.

Should my HCG Level be checked routinely?

It is not common for doctors to routinely check your hCG levels unless you are showing signs of a potential problem.

However, a health care provider may recheck your levels if you are bleeding, experiencing severe cramping, or have a history of miscarriage.

I have a history of a pregnancy loss. What can I expect from my HCG Levels?

Most women can expect their Human Chorionic Gonadotrophin (hCG) levels to return to a non-pregnant range about 4 – 6 weeks after a pregnancy loss has occurred.

This time can change depending on how the loss occurred (spontaneous miscarriage, D & C procedure, abortion, natural delivery) and how high the levels were at the time of the loss. Healthcare providers will usually continue to test hCG levels after a pregnancy loss to ensure they return back to <5.0.

Can Anything Interfere With My hCG Levels?

If you get a positive result for hCG, you are most likely pregnant.

False positives are extremely rare. However, there are some conditions that may cause a false positive – such as certain types of cancer and early miscarriage.

The presence of some antibodies may also interfere with hCG test results.

Medications that contain hCG may interfere with hCG levels, as well. These medications are often used in fertility treatments, and your healthcare provider should advise you on how they may affect a test.

All other medications such as antibiotics, pain relievers, contraception or other hormone medications should not have any effect on a test that measures hCG.

Levels of hCG in your blood don’t provide a diagnosis of anything. They can only suggest that there are issues to look into. In case of any doubts, it is always recommended to consult with your doctor.

I did all the research I could out of curiosity because my wife is pregnant and I wanted to understand it in a better way to support her. Also, this research was oriented to help me in making more informed decisions wherever needed.  I am not a certified medical practitioner or healthcare professional.

Sources:
 American Pregnancy Association (Human chorionic gonadotropin (HCG): The Pregnancy Hormone).
NHS Choices (UK) (How soon can I do a pregnancy test?).

St Vincents Hospital Sydney
 (hCG (human Chorionic Gonadotrophin).

WebMD (Human chorionic gonadotropin)

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