hCG Levels in pregnancy: Purpose & week-by-week chart

What is human chorionic gonadotropin (hCG)?

Human chorionic gonadotropin, or hCG, is a hormone best known for its role in pregnancy. hCG is a little more complex and is actually a family of closely-related molecules that serve a variety of purposes in our bodies. [1] During pregnancy, hCG is primarily produced just after conception by special cells in the embryo that later become part of the placenta. One of the purposes of hCG during pregnancy is to support the corpus luteum, which maintains the lining of the uterus and supports the development of the fetus early in the pregnancy until the placenta gradually takes over [2]. 

Beyond supporting the corpus luteum, hCG plays a wider role in pregnancy. It helps the placenta implant deeply into the lining of the uterus, supports the growth of the blood vessels that supply the placenta, encourages the mother's immune system to welcome the developing fetus, and helps keep the uterine muscle relaxed during pregnancy. hCG has even been linked to the nausea and vomiting some people experience early on, as receptors for hCG are present in parts of the brain involved in nausea. [1]

Although hCG is best known as the hormone of pregnancy, it is also produced in small amounts by the pituitary gland in non-pregnant women, where it works alongside luteinizing hormone (LH) to support ovulation and the menstrual cycle. [1] hCG levels can also rise as women approach menopause, when the pituitary becomes more active. In rare cases, elevated hCG in someone who is not pregnant can be observed with certain cancers.

hCG levels & pregnancy

hCG is primarily used to detect pregnancy, for example, when using at-home pregnancy tests. Levels of hCG, however, can vary widely from woman to woman and from pregnancy to pregnancy. During a pregnancy, hCG levels typically double every 48 hours for the first 8 weeks, peak around week 10, then decline until around week 20 and remain low until delivery. [1] 

When does the body make hCG?

hCG starts to circulate in the female body after implantation, but it usually takes at least a week for the levels to be detectable on a urine test. While hCG increases rapidly after implantation, individual levels can vary widely from person-to-person, even in those early days and weeks [3].  

hCG is usually detectable between 6 and 14 days after fertilization, in both urine and blood [3]. However, it’s recommended to wait longer, until the first day of your missed period, to take most  at-home pregnancy tests. Taking a pregnancy test too soon risks a false negative, if your body hasn’t been given enough time to produce hCG at detectable levels. Always check the guidelines on the specific tests before use.

How do hCG levels impact pregnancy? 

 Since hCG levels are individual and pregnancy is a complex process with many parts, doctors typically do not use hCG alone to diagnose any conditions during a pregnancy. However, high or low hCG levels have been linked to a few different things. 

Low hCG levels before six weeks can be used to predict the health and outcome of a pregnancy [3]. Additionally, some studies have found that hCG levels are higher in multifetal pregnancies (twins, triplets, or other multiples) [4]. Similarly, some studies have observed that women carrying girls have higher hCG levels on average in the second trimester than those carrying boys, but those differences were not seen in the first trimester [3].

Testing for hCG in pregnancy

There are two main ways of testing for hCG: urine and blood tests. Most urine tests are designed to tell you whether hCG is present above a certain concentration, signaling that you are pregnant. Urine tests can be done at home in a few minutes, while blood test results typically take longer. Blood tests, also called serum tests, are more sensitive and specific, capable of telling you the amount of hCG directly in your blood. Blood test results, however, typically take longer. [1]

How to test hCG levels?

Determining hCG levels is most often done with a blood test administered and analyzed by a laboratory technician or doctor. The detailed data can provide important information on your health, in a variety of situations. Checking levels of hCG is a normal part of care during a pregnancy. hCG levels can help your care team assess whether a pregnancy is proceeding normally and also can help determine how far along a pregnancy is. In case of pregnancy loss, it can also be used as a monitoring tool. [1] 

The table below shows how hCG levels change throughout the course of pregnancy and the most common range. Keep in mind that all pregnancies are different, and hCG levels by week can vary greatly from individual to individual. [5] 

Talk to your healthcare professional if you have concerns or questions about hCG.. Your doctor will also be on the lookout for unexpectedly high or low hCG levels. Rather than provide a diagnosis on their own, unusually high or low levels of hCG will likely prompt further monitoring or testing.

What do high hCG levels mean?

In the first trimester, hCG levels are at their highest. In the second trimester, hCG levels have been more closely studied for any possible links to pregnancy-related conditions. During the second trimester, higher-than-normal hCG levels might be linked with gestational hypertension (high blood pressure), preeclampsia, low birth weight, and preterm delivery, but the evidence remains uncertain [6]. If your care team suspects you are at risk of any of these, they will likely monitor your pregnancy more closely and provide additional guidance. 

What about low levels?

Lower than normal levels of hCG in the first trimester are most commonly associated with pregnancy loss. [7] Lower hCG levels have also been linked to preeclampsia in some studies but on their own, hCG levels are not enough to provide a diagnosis of preeclampsia. Instead they can signal to your nurse or doctor that further testing or monitoring might be needed [8]. 

If you have any questions or concerns about hCG levels, it’s a good idea to talk to a healthcare professional to learn more about these in relation to your specific circumstances.

What happens to hCG levels after a pregnancy loss?

If you’ve experienced pregnancy loss, you’re not alone. Early miscarriage is the most common type of loss with an estimated 80% of all miscarriages happening in the first trimester) [9]. While it’s very difficult to know exactly why this type of loss happens, you may find it helpful to know that around 85% of women who experience a first early pregnancy loss will go on to have a successful pregnancy [10]. 

After experiencing a pregnancy loss, it’s important to remember that hCG levels will not drop immediately, and the rate of decline is dependent on both the individual and how far along the pregnancy was. For this reason, an at-home pregnancy test can still show a positive result more than a week after a pregnancy loss, as hCG levels eventually return to zero [7]. hCG levels can be monitored after a pregnancy loss to verify that they return to non-pregnant levels (less than 5 mIU/mL). This helps doctors understand if further treatment might be needed. If you suspect you have miscarried, it's important to consult with your healthcare team for both medical guidance and support. 

When to see a healthcare professional?

If you are pregnant and have any questions or concerns about your pregnancy or any test results you have received, it’s important to talk with your nurse or doctor. Similarly, if you think you might have experienced an early pregnancy loss, your healthcare team can assist in your recovery and provide guidance, especially if you are still trying to conceive. 

Planning and following a pregnancy with Natural Cycles

If you are trying to conceive or have recently found out you are pregnant, you find yourself with more questions than answers. Did you know that Natural Cycles can help? NCº Plan Pregnancy will alert you when you are the most likely to conceive and even let you know when it’s time to take a pregnancy test. NCº Follow Pregnancy offers tailored prenatal guidance and comprehensive pregnancy tracking to help you stay informed and empowered. After birth, you can even use NC° Postpartum as your body and mind recover and adjust to this new stage of life. Whatever stage of the journey you’re on — find out how Natural Cycles can support you, today!