Why hCG Doubling Times Are Important in Early Pregnancy

woman getting blood drawn and nurse applying cotton ball
Westend61/Getty Images

When your physician talks about hCG, they are referring to the hormone human chorionic gonadotropin, which the placenta produces during pregnancy. That's why it's called "the pregnancy hormone."

The conventional wisdom is that in early pregnancy, the level of hCG in a quantitative hCG blood test should double about every two to three days. But if yours is rising more slowly, don't panic quite yet. The numbers are just a guideline, and the change in level may be more important than the actual number.

How Early Can You Detect hCG?

A blood test can first detect hCG about 11 days after you conceive. A urine test, those pregnancy test sticks you buy at the drugstore, can detect hCG about 12 to 14 days after conception.

The measurement of hCG is in milli-international units per milliliter, and an hCG level above 25mIU/ml is a positive indicator of pregnancy. The two common types of hCG tests are a qualitative test, which detects the presence of the hormone in your blood, and a quantitative test, which measures the amount in your blood.

Why Check hCG Doubling Times?

Doubling times for hCG are a good way to check whether a pregnancy is progressing normally until about six or seven weeks after your last menstrual period. In a typical pregnancy, your hCG levels double every 72 hours.

This 72-hour period increases to about every 96 hours as you get further along. The level of this hormone peaks during the first 8 to 11 weeks of your pregnancy, then declines and levels off.

After 5 to 6 weeks gestation, ultrasounds become the best tool for getting information on how the pregnancy is developing and are much more accurate than hCG numbers. Women with low numbers can go on to have a normal pregnancy and a perfectly healthy baby. Note that hCG levels are not an appropriate way to date a pregnancy (that is, to determine conception and from there, estimated due date).

What Do Slow-Rising hCG Doubling Times Mean?

Slow-rising hCG doubling times can be a sign of miscarriage or symptom of ectopic pregnancy, but this is not always true. The two- to three-day guideline holds true in 85% of normal pregnancies. So that means about 15% of viable pregnancies may have slower hCG doubling times.

What Do High hCG Levels Mean?

High hCG levels also have meaning. High levels can indicate:

  • A miscalculated conception date
  • A molar pregnancy
  • A multiple pregnancy (twins or more)

Lowest Rise Recorded for a Normal Pregnancy

In a 2004 study, researchers found that hCG could increase as little as 53% over a period of two days even in a normal pregnancy, although slow-rising hCG levels are less common in normal pregnancies. The 53% increase was the slowest rise ever recorded for hCG levels in early pregnancy and slow-rising hCG levels usually do mean complications.

Was this page helpful?
Article Sources
Verywell Family uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Barnhart KT, Sammel MD, Rinaudo PF, Zhou L, Hummel AC, Guo W. Symptomatic patients with an early viable intrauterine pregnancy: HCG curves redefined. Obstet Gynecol. 2004;104(1):50-5. doi:10.1097/01.AOG.0000128174.48843.12

Additional Reading