What are the expected human chorionic gonadotropin (hCG) levels after a miscarriage and how long does it take for them to decrease to undetectable levels?

From the Guidelines

After a miscarriage, human chorionic gonadotropin (hCG) levels typically decrease at a rate of about 50% every 48 hours, though this can vary between individuals. For most women, hCG becomes undetectable in blood tests within 4-6 weeks after a complete miscarriage. However, the timeframe depends on how high the hCG levels were at the time of miscarriage - higher initial levels will take longer to decline to zero. Some key points to consider:

• For early pregnancy losses, hCG may become undetectable within 1-2 weeks, while later miscarriages might take 2 months or more 1.
• Healthcare providers often monitor hCG levels after miscarriage to ensure they're decreasing appropriately, as persistent elevation could indicate retained pregnancy tissue, incomplete miscarriage, or in rare cases, gestational trophoblastic disease.
• If levels plateau or rise, further evaluation and possibly additional treatment may be needed.
• The rate of decline is important - slower than expected decreases might require follow-up ultrasounds or procedures like dilation and curettage (D&C) to remove remaining tissue.
• This monitoring helps ensure complete resolution of the pregnancy and allows for appropriate timing of future conception attempts. It's also worth noting that qualitative pregnancy tests can remain positive for several weeks after termination of pregnancy because hCG can be present for several weeks after delivery or abortion (spontaneous or induced) 1. In terms of specific guidelines, a health-care provider can be reasonably certain that a woman is not pregnant if she has no symptoms or signs of pregnancy and meets any one of the following criteria, including being ≤7 days after spontaneous or induced abortion 1. Overall, the key takeaway is that hCG levels should be monitored after a miscarriage to ensure they are decreasing appropriately, and any concerns or abnormalities should be discussed with a healthcare provider.

From the Research

Expected hCG Levels After a Miscarriage

• The expected human chorionic gonadotropin (hCG) levels after a miscarriage vary depending on the initial hCG value and the gestational age at the time of miscarriage 2, 3.
• A study published in 2004 found that the rate of decline in hCG levels ranged from 21% to 35% at 2 days and 60% to 84% at 7 days, depending on the initial hCG value 2.
• Another study published in 2017 found that the mean serum hCG decline after complete medical abortion was 70.0% on Day 3 and 91.4% on Day 5, with no difference in percent hCG decline stratified by initial hCG or gestation 3.

Time for hCG Levels to Decrease to Zero

• The time it takes for hCG levels to decrease to undetectable levels after a miscarriage can vary, but most studies suggest that it can take several days to a week or more 2, 3, 4.
• A study published in 2017 found that the median percentage change in total βhCG levels (%ΔβhCG) for cases with no sac at transvaginal ultrasound was 97.65% at 7-9 days after misoprostol treatment 4.
• Another study published in 2022 found that early pregnancy loss treatment success was associated with a greater percent hCG level decline, but no threshold was able to predict success, and additional research is needed to understand hCG trends after medical management of early pregnancy loss 5.

Factors Affecting hCG Decline

• The initial hCG value and gestational age at the time of miscarriage can affect the rate of decline in hCG levels 2, 3.
• A study published in 2013 found that serum β-hCG measurement and ultrasound examination were both useful in predicting complete abortion after medical induction, but β-hCG should be used as supplements to clinical assessments 6.
• The rate of hCG decline can also be influenced by the type of miscarriage treatment used, such as medical or surgical management 3, 4.