Human chorionic gonadotropin (HCG) is a hormone produced by the placenta during pregnancy, supporting the uterus and uterine lining. It is detected by home pregnancy tests and measured in blood tests to confirm pregnancy. Following a miscarriage, HCG production typically ceases, and levels are expected to gradually decline as the body returns to a non-pregnant state.
Normal HCG Decline After Miscarriage
After a miscarriage, HCG levels do not immediately drop to zero; they usually decrease gradually over a period of weeks. Research indicates HCG levels can decline by approximately 50% within 48 hours and 66% to 87% within seven days following a miscarriage.
The time it takes for HCG to become undetectable varies among individuals, typically ranging from four to six weeks. For some, particularly after an early pregnancy loss, HCG levels may normalize within days or a couple of weeks. However, in cases of later miscarriages, it could take up to two months or more for HCG to reach non-pregnant levels. The initial HCG level at the time of miscarriage and the completeness of the miscarriage can influence the rate of decline.
Reasons for Unexpected HCG Levels
While HCG levels are expected to decline after a miscarriage, they may not fall as anticipated or could even rise. This can indicate the body has not fully returned to its pre-pregnancy state or that other medical conditions are present.
Incomplete Miscarriage
An incomplete miscarriage is a common reason for HCG levels not declining as expected. This occurs when some pregnancy tissue, also known as retained products of conception, remains in the uterus after the miscarriage. The lingering tissue can continue to produce HCG, causing levels to decrease more slowly or to plateau. Symptoms such as prolonged or heavy vaginal bleeding, persistent cramping, or the passage of blood clots can suggest an incomplete miscarriage. An ultrasound scan may reveal a thickened endometrial lining, an intracavitary mass, or increased vascularity within the uterus.
Gestational Trophoblastic Disease (GTD)
Gestational trophoblastic disease (GTD) is another reason for unexpected HCG patterns. This rare group of conditions involves abnormal cell growth from the tissue that would normally form the placenta. This includes conditions such as molar pregnancy (hydatidiform mole) and, in rarer cases, choriocarcinoma. In complete molar pregnancies, HCG levels can be significantly elevated, sometimes exceeding 100,000 mIU/mL, or they may plateau or rise after a miscarriage. Symptoms associated with GTD can include severe nausea and vomiting, unusual vaginal bleeding, or a uterus that is larger than expected for the gestational age. Diagnosis often involves ongoing HCG monitoring and ultrasound imaging, which can show a characteristic “snowstorm appearance” in cases of complete molar pregnancy.
New Pregnancy
In some situations, a new pregnancy might occur very soon after a miscarriage, leading to a rise in HCG levels. Ovulation can resume as early as two weeks following a miscarriage, making it possible to conceive again before HCG from the previous pregnancy has fully cleared. This can result in elevated HCG readings that are due to a new gestation rather than residual HCG from the prior loss.
Ectopic Pregnancy
An ectopic pregnancy, where a fertilized egg implants outside the uterus, typically in a fallopian tube, can also cause atypical HCG patterns. In an ectopic pregnancy, HCG levels may rise more slowly than in a typical pregnancy, or they might plateau or even initially decrease before rising again. This condition can present with symptoms such as abdominal pain and vaginal bleeding, and it requires prompt medical attention due to the potential for serious complications.
Medical Guidance and Next Steps
Monitoring HCG levels after a miscarriage is common to confirm the complete resolution of the pregnancy and to identify any complications. Healthcare providers often conduct serial blood tests to track the decline of the hormone. This helps ensure that levels are decreasing appropriately and reaching non-pregnant ranges.
Contact a doctor if HCG levels do not decline as expected, or if they plateau or begin to rise. Additionally, persistent or worsening symptoms such as heavy bleeding, severe abdominal pain, fever, or unusual discharge warrant immediate medical consultation. These signs can indicate an underlying issue that requires medical intervention.
To determine the cause of unexpected HCG levels, a doctor may recommend further diagnostic procedures. These often include additional HCG blood tests to observe the trend of the hormone over time. An ultrasound, particularly a transvaginal ultrasound, is frequently used to visualize the uterus and surrounding areas for any remaining pregnancy tissue or other abnormalities. Depending on the diagnosis, treatments can range from medical management with medication to surgical procedures like dilation and curettage (D&C), which involves removing tissue from the uterus. Seeking professional medical advice ensures proper diagnosis and management.