When is the hCG titer in the blood considered to be too low and when is it considered to be slow rising?
The measurement of serum hCG concentrations over several days, usually 48-72 hours apart is important to identify a normal from an abnormal early pregnancy. This is usually done before an ultrasound can be of value to assess the viability of the pregnancy.Comparing changes in hCG titers with those of established expected curves can help the doctor determine what to do about the pregnancy and how to counsel the patient. However, there are many limitations to the serial assessment of hCG titers and the titers should never be used exlusively to replace clinical judgment based on symptoms or signs.
Calculate your hCG levels with the BabyMed hCG Calculator.
- An hCG level below 5 mIU/ml is considered "not pregnant"
- An hCG level above 25 mIU/ml is considered "pregnant".
- An hCG level between 5-25 mIU/ml requires a follow-up test to confirm what it could be.
- At hCG levels in early pregnancy below 1,200 mIU/ml the hCG usually doubles every 48-72 hours.
- At hCG levels in early pregnancy below 1,200 mIU/ml the hCG should normally increase by at least 60% every two days.
- If the hCG rises less than 60% in 2 days then that is considered "slow rising".
- Between 1,200 and 6,000 mIU/ml serum hCG levels in early pregnancy, the hCG usually takes 72-96 hours to double
- Above 6,000 mIU/ml, the hCG often takes over four or more days to double.
- After 9-10 weeks of the pregnancy hCG levels normally decrease
There are several possibilities when a Beta hCG level rises slower than expected.
- Sometimes a normal pregnancy can have a slower than expected hCG titer, and the next test will usually show a normal rise. It is quite possible to have “slow to rise” hCG levels and go on to have a normal pregnancy.
- Most commonly, a slower than expected rise indicates a pregnancy that may be failing, such as a miscarriage or a 'blighted ovum.'
- Another possibility is an ectopic pregnancy, which is a pregnancy that somehow got outside of the uterus and is growing in the fallopian tube. IVF increases the risk of ectopic pregnancy over natural conception.
Expected minimal percent of hCG decline for non-viable pregnancies
|Initial hCG (MIU/ml)||% Decline after 2 days||% Decline after 4 days|
Adapted from Barnhart et al., Ob Gyn 2004 (9); and Chung et al., Fertil Steril 2006 (10).
Testing at the same lab and in multiples of two days apart allows us to more easily interpret the levels and eliminates the possibility of variation between labs. Now that BhCG testing is standardized, this has become less of an issue.
Many doctors use hCG values as only a reference. Depending on the estimated gestational age, other testing such as transvaginal or abdominal ultrasound is also used to determine pregnancy progress.