Is Miscarriage Imminent If hCG Is Not Doubling?

The journey of pregnancy often begins with a positive urine pregnancy test detecting human chorionic gonadotropin (hCG), the hormone produced by the placenta. During a normal pregnancy, the levels of hCG continue to increase—in fact, levels double every two to three days in the very early weeks of pregnancy.

Seeing those numbers rise can be comforting, but what if your hCG level is not doubling in early pregnancy? Many pregnant women begin to that this is a sign of impending miscarriage.

Measuring hCG Levels

Urine tests, whether done at home or the doctor's office, only detect the presence of hCG, not the amount. Blood tests can be either qualitative (determining whether hCG is in your blood) or quantitative (determining exactly how much hCG is in your blood). Your doctor may monitor your hCG level in early pregnancy if you are experiencing signs and symptoms of miscarriage, such as bleeding and cramping.

In addition to measuring your hCG level, your doctor may also perform an ultrasound if the hCG level is high enough (at least 1500 mIU/ml to 2000 mIU/ml) to detect a gestational sac. Slow-rising hCG blood levels can also be a sign of an ectopic pregnancy, which is another reason why a doctor might follow serial hCG levels.

Patterns of hCG in Early Pregnancy

In the majority of normal pregnancies, the level of hCG will double every two to three days during the first four weeks of pregnancy.

If the hCG level is increasing, but not doubling at least every three 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%. This means that an hCG level that increased by about 75% (rather than by 100%, which is doubling) after three days could theoretically still be normal. If your hCG levels aren't exactly doubling but are still increasing by a significant amount, then you may still have a healthy pregnancy.

The rate of hCG doubling slows as your pregnancy progresses past the first four weeks. After the hCG level passes roughly 1200 mIU/ml, it tends to take longer to double. By week six or seven, for instance—about halfway through the first trimester—it may take about three and a half days to double.

If hCG levels are actually decreasing (rather than increasing more slowly than usual) in the early weeks of pregnancy, that is unfortunately a more reliable sign of miscarriage.

After you hit an hCG level of 6000 mIU/ml, it may be four days or more until it doubles. The hCG level tends to peak between week eight and week 11 of gestation. But these are estimates—the exact time frame is different for every pregnancy. 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 vaginal bleeding, cramping, or the passing of any tissue through the vagina. A miscarriage can be difficult to handle, both physically and emotionally. If you do experience one, give yourself time to recover and grieve. Your doctor can likely direct you toward support groups that can help you cope.

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