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 slower, don't panic quite yet.
Slow-rising hCG doubling times can be a possible sign of miscarriage or symptom of ectopic pregnancy, but this is not always true. According to the American Pregnancy Association, 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. In one 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. (Keep in mind that the 53% increase was the slowest rise ever recorded for hCG levels in early pregnancy and that slow-rising hCG levels do mean complications in many cases.)
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. After that point, hCG doubling times begin to slow and ultrasounds become the best tool for getting information on how the pregnancy is developing.
Sources:
American Pregnancy Association, "Human Chorionic Gonadotropin (hCG): The Pregnancy Hormone." July 2007. Accessed 17 Jan 2008.
Barnhardt, Kurt T., Mary D. Sammel, Paolo F. Rinaudo, Lan Zhou, Amy C. Hummel, and Wensheng Guo, "Symptomatic Patients With an Early Viable Intrauterine Pregnancy." Obstetrics & Gynecology 2004. Accessed 14 Jan 2008.
