Dropping hCG Levels and Miscarriage

Pregnancy test on edge of bathroom sink, close-up
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In the first trimester, levels of human chorionic gonadotropin, a pregnancy hormone commonly known as hCG, are supposed to increase over time in normal pregnancies. Usually, hCG levels are expected to double every two to three days in early pregnancy.

hCG is made by placental cells that provide nourishment to the egg after it has been fertilized and attaches to the uterine wall. It is the same hormone that home pregnancy tests can detect in urine about 12 to 14 days after conception. Blood tests are more sensitive and can detect the hormone as early as 11 days after conception.

In most healthy pregnancies, hCG levels, measured in milli-international units per milliliter (mIU/ml), will double about every 72 hours, which is why physicians will order two consecutive tests taken two to three days apart. hCG will reach its peak level in the first 8 to 11 weeks of a pregnancy, after which it will decline and level off for the rest of the pregnancy. Further into a pregnancy, when hCG levels are higher, it can take up to 96 hours for them to double.

Normal hCG Levels

hCG levels can vary dramatically, from woman to woman and from pregnancy to pregnancy. Generally, an hCG level less than 5 mIU/ml means a woman is not pregnant and anything above 25 mIU/ml indicates a pregnancy has occurred.

While the below ranges give an idea of what is considered normal, the results of one hCG blood test mean very little. Rather, the change in the level between two consecutive tests done 2 to 3 days apart is much more telling of how a pregnancy may progress.

Weeks From Last Menstrual Period hCG Level (in mIU/ml)
3 5 to 50
4 5 to 426
5 18 to 7,340
6 1,080 to 56,500
7-8 7,6590 to 229,000
9-12 25,700 to 288,000
13-16 13,300 to 254,000
17-24 4,060 to 165,400
25-40 3,640 to 117,000

What If Your hCG Levels Have Dropped?

Women whose hCG level falls over a period of two to three days in the first trimester in two quantitative hCG blood tests are often advised that this means an impending miscarriage. This is especially true for women with other miscarriage symptoms, such as vaginal bleeding during pregnancy.

Decreasing hCG levels later in pregnancy, such as the second and third trimester, are probably not a cause for concern. Most doctors do not check serial quantitative hCG levels for purposes of evaluating the progress of a pregnancy after the first trimester, although single hCG levels might be checked as a part of the AFP prenatal screening test.

hCG Levels After Miscarriage

After a pregnancy loss has occurred, hCG levels will return to a nonpregnant range (less than 5 mIU/ml) between four and six weeks later. However, the time it takes for hCG levels to return to this range may depend on how the loss occurred, for example, whether by spontaneous miscarriage or dilation & curettage (D&C) as well as how high the levels were when the miscarriage occurred.

It is typical for physicians to continue to test hCG levels after miscarriage until they return to the nonpregnant range.

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