Human Chorionic Gonadotropin (HCG) is a hormone produced during pregnancy. It supports early pregnancy. HCG levels track pregnancy progression and viability. Understanding HCG levels in healthy pregnancies and during miscarriage helps individuals and healthcare providers navigate these complex situations.
HCG in Healthy Pregnancy
Human Chorionic Gonadotropin originates from the cells that will eventually form the placenta, specifically after the fertilized egg implants in the uterine wall. In a healthy, early pregnancy, HCG levels typically double approximately every 48 to 72 hours. This rapid increase is an indicator of a progressing pregnancy.
HCG levels continue to rise, usually peaking around 8 to 11 weeks of gestation. After this peak, the levels generally decline or plateau for the remainder of the pregnancy. Normal HCG ranges are broad and vary significantly between individuals and pregnancies. A single HCG measurement is less informative than observing the trend of levels over several days.
HCG Levels During Miscarriage
During a miscarriage, the pattern of HCG levels often deviates from that of a healthy pregnancy, indicating non-viability. Instead of the expected rapid doubling, HCG levels might plateau, rise more slowly than anticipated, or begin to decline. These changes signal that the body is no longer supporting the pregnancy’s growth.
In a complete miscarriage, HCG levels typically show a rapid and steady decline as the pregnancy tissue has been fully expelled. The levels decrease significantly, often by around 50% every 48 hours. This pattern indicates a resolution of the pregnancy.
With an incomplete miscarriage, some pregnancy tissue may remain in the uterus. In these cases, HCG levels might decline more slowly or plateau, rather than dropping sharply. The persistence of pregnancy tissue continues to produce some HCG, preventing a rapid return to non-pregnant levels.
In scenarios such as a missed miscarriage or a blighted ovum, HCG levels can be confusing as they may initially rise, similar to a viable pregnancy. A blighted ovum occurs when a fertilized egg implants but an embryo does not develop, or stops developing very early. The placental tissue continues to produce HCG, leading to positive pregnancy tests and symptoms despite no viable embryo. Eventually, HCG levels will plateau or slowly decline, indicating the pregnancy’s non-viability.
HCG Monitoring After Miscarriage
After a miscarriage, monitoring HCG levels ensures all pregnancy tissue has passed and the body returns to a non-pregnant state. HCG levels should steadily decline until they reach a non-pregnant level, typically below 5 mIU/mL. For many women, this return to baseline occurs within 4 to 6 weeks, though the exact timeframe can vary.
HCG decline rate after miscarriage is influenced by gestational age and initial HCG level. Higher initial levels or later gestational age mean a longer period for HCG to become undetectable. Following a complete miscarriage, HCG levels may decrease by 35% to 50% within two days and 66% to 87% within seven days.
Persistent or rising HCG levels after a miscarriage could indicate retained pregnancy tissue. In rare instances, these patterns might also suggest conditions like gestational trophoblastic disease (GTD), a condition where abnormal cells grow in the uterus after conception. Medical guidance is important to ensure proper resolution and address any complications.