What to Know About HCG Levels in Pregnancy (original) (raw)

Human chorionic gonadotropin (hCG) is one of the most well-known pregnancy hormones. It's produced by the placenta after the embryo implants into the lining of the uterus. HCG is detectable in your urine starting around 10 days after conception, and the presence of the hormone leads to a positive home pregnancy test.

While you may be familiar with hCG, you might not understand exactly how it fluctuates throughout pregnancy. Here, we break down the expected hCG levels by week, and explain what hCG patterns indicate about the health of the fetus.

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How hCG Levels Change by Week

Your hCG levels will surge in early pregnancy as your embryo develops. While most hormones continue to rise throughout the 40-week journey, hCG doesn't follow that pattern. Instead, hCG levels usually double in concentration every 29–53 hours during the first several weeks of pregnancy. After about 8 to 10 weeks, hCG levels begin to fall and eventually stop progressing.

"This means that at the beginning of pregnancy, your hCG number (measured in mIU/ml or IU/l ) might be 2. It'll then move to 4, 8, and 16, and then it really picks up speed, moving into the 25,000 to 50,000 range," says Elisa Ross, MD, an OB-GYN at Cleveland Clinic Hillcrest Hospital. "When it gets to around 100,000, it turns around and goes down again. For the rest of your pregnancy, your hCG level will likely remain around 10,000."

Why Does hCG Stop Rising?

Most experts theorize that the reason for changes in hCG levels is that, at a certain point in the pregnancy, the placenta takes over, making the hormones estrogen and progesterone. This means hCG is no longer needed to stimulate the ovary to make hormones, says Dr. Ross.

Week-by-Week hCG Levels Chart

There's a wide range of healthy hCG levels. Because the normal range is so large, it's often hard to tell much about pregnancy from just one hCG measurement, says Michele Hakakha, MD, an obstetrician and co-author of Expecting 411.

Health care providers often care more about the trends in hCG than the actual numbers. If hCG is rising or doubling as it should, there's usually no cause for alarm. On the other hand, if hCG levels are slow-rising or falling in early pregnancy, it could indicate miscarriage or ectopic pregnancy.

Refer to this chart for average hCG levels per week.

Weeks Of Pregnancy Average hCG Levels
3 weeks 5 - 72 mIU/mL
4 weeks 10 -708 mIU/mL
5 weeks 217 - 8,245 mIU/mL
6 weeks 152 - 32,177 mIU/mL
7 weeks 4,059 - 153,767 mIU/mL
8 weeks 31,366 - 149,094 mIU/mL
9 weeks 59,109 - 135,901 mIU/mL
10 weeks 44,186 - 170,409 mIU/mL
12 weeks 27,107 - 201,165 mIU/mL
14 weeks 24,302 - 93,646 mIU/mL
16 weeks 8,904 - 55,332 mIU/mL
18 weeks 9,649 - 55,271 mIU/mL

Source: MedlinePlus

How Do You Test hCG Levels?

Home pregnancy tests detect hCG in your urine. While a home pregnancy test may appear darker with higher hCG levels, in general, urine tests only detect the presence of hCG and can't tell you how much hCG is present.

"Urine pregnancy tests are very accurate. They can usually detect an hCG level of at least 20–50 mIU/mL," says Brennan Lang, MD, an OB-GYN at Baylor Obstetrics and Gynecology at Texas Children's Pavilion for Women. If the results are positive, he says you need to confirm a pregnancy with a pelvic ultrasound, a pelvic exam, or a blood test at the doctor's office.

"The blood test does have a lower threshold to be positive, measuring levels as low as about 1 to 5 mIU/mL," says Dr. Lang. "However, one single blood test is not always very helpful. Usually, we need at least two measurements (at least 48 hours apart or more) to begin to understand how a pregnancy is progressing." That's because trends in hCG levels are more important than the numbers themselves in determining a healthy pregnancy.

What Causes Low hCG Levels?

Causes of low, slow-rising, or dropping hCG levels might include the following.

Tip

Your due date is commonly calculated from the first day of your last menstrual period (LMP) and assumes a 28-day cycle with ovulation on day 14. Incorrect dating is more likely if you have irregular cycles or your cycles are significantly longer or shorter than 28 days.

What Causes High hCG Levels?

According to Dr. Lang, extremely high levels of hCG (greater than 100,000 mIU/mL) may represent an abnormal pregnancy. Causes may include the following: