Is Miscarriage Imminent if hCG Is Not Doubling?

Find out what the results of this prenatal exam really mean

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The delicate journey of pregnancy begins with the detection of human chorionic gonadotropin (hCG), the hormone produced by the placenta, by at-home, urine-based pregnancy tests.

During a normal pregnancy, the levels of hCG continue to increase—in fact, they double every two to three days in the very early days of pregnancy.

But what if your hCG level is not doubling in early pregnancy. Is this a sign of miscarriage?

hCG Levels and Miscarriage

The short, and perhaps frustrating answer is maybe, but maybe not.

Human chorionic gonadotropin (hCG) is a hormone that is created in the cells of your placenta when you are pregnant, and its presence in your body is the reason that your at-home, urine-based pregnancy test, as well as your in-office, blood-based pregnancy test, are positive.

Your doctor may monitor your hCG level throughout your early pregnancy if you are experiencing early signs and symptoms of a miscarriage like bleeding and cramping. Blood tests that check for hCG can be either qualitative (and simply tell you whether hCG is in your blood or not) or quantitative (and tell you exactly how much hCG is in your blood). 

It's important to note that in addition to measuring your hCG level, your doctor may also perform an ultrasound, if the hCG level is high enough (at least 1500 to 2000) to detect a gestational sac.

Furthermore, besides a nonviable pregnancy, slow-rising hCG blood levels may also be a sign of an ectopic pregnancy, which is another reason why a doctor may follow serial hCG levels. 

hCG Patterns in Early Pregnancy

According to the American Pregnancy Association, in about 85 percent of normal pregnancies, the level of the hormone hCG will double every two to three days during early pregnancy, usually throughout the first four weeks.

 When the hCG level is increasing but not doubling at least every 3 days, this may be a warning sign of an impending miscarriage, but not necessarily.

For instance, in one study that monitored hCG increase patterns in early pregnancy, the lowest documented two-day hCG increase in a normal pregnancy was 53 percent. This means that an hCG level that increased by about 75 percent (rather than by 100 percent) after three days, could theoretically, still be normal. In other words, if your hCG levels aren't exactly doubling but are still increasing by a significant amount, then you may still have a healthy pregnancy.

If your hCG levels are increasing but not doubling in early pregnancy, your doctor will likely monitor your pregnancy more closely. For example, your physician might ask you to come in for more frequent blood tests to keep checking your hCG level. 

The rate of hCG doubling slows down as your pregnancy progresses, so slower hCG doubling times are normal if you're past the first four weeks or so of pregnancy. As your pregnancy goes on and your hCG level passes roughly 1,200 mIU/ml, it tends to take longer to double. By week six or week seven, for instance—about halfway through your first trimester—it may take about three and a half days to double.

Finally, an important caveat is if your hCG level not only isn't doubling but is actually decreasing in early pregnancy, that is, unfortunately, a more reliable sign of a miscarriage. 

hCG Levels in the Second Half of the First Trimester

After you hit an hCG level of 6,000 mIU/ml, it may be four days or more until it doubles. Your hCG level tends to peak between week eight and week 11 of gestation. But keep in mind, these are estimates—the exact time frame is different for every woman. By the second half of the first trimester, ultrasound is more reliable than hCG levels for judging whether a pregnancy is viable.

A Word From Verywell

It's important to call your doctor immediately if you notice any vaginal bleeding, cramping, or the passing of any tissue through the vagina.

A miscarriage can be extremely difficult to handle, both physically and emotionally, so if you do experience one, give yourself an appropriate amount of time to recover and grieve. Your doctor can likely direct you toward support groups that can help you cope. 

Sources:

American Pregnancy Association. (2017). Human Chorionic Gonadotropin (HCG): The Pregnancy Hormone. 

Seeber BE. What Serial hCG Can Tell You, and Cannot Tell You, About an Early Pregnancy. Fertil Steril. 2012 Nov;98(5):1074-7.

Visconti K, Zite N. hCG in Ectopic Pregnancy. Clin Obstet Gynecol. 2012 Jun;55(2):410-7.

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