Human Chorionic Gonadotropin (HCG), often called the “pregnancy hormone,” is produced during gestation and detected by pregnancy tests. After a miscarriage, HCG levels are expected to decline. However, if HCG levels remain elevated or rise, it indicates an unexpected medical situation requiring attention. This article explores the reasons for HCG fluctuations after pregnancy loss and outlines the diagnostic and treatment approaches healthcare providers use.
Expected HCG Decline After Miscarriage
During pregnancy, the placenta produces HCG, with levels rising rapidly in early weeks. After a miscarriage, the source of HCG production is no longer viable, and the body eliminates the hormone. The rate of HCG decline varies based on the initial HCG level and gestational age at the time of miscarriage.
HCG levels typically decrease by about 50% every 48 hours following a complete miscarriage. Most individuals’ HCG levels return to non-pregnant levels, usually below 5 mIU/mL, within four to six weeks. For those with higher initial HCG levels or later gestational age miscarriages, this process may take longer. Monitoring this decline is important to confirm the complete resolution of the pregnancy.
Common Reasons for Persistent or Rising HCG
If HCG levels do not decline as expected or begin to rise after a miscarriage, it suggests HCG-producing tissue may still be present. Several medical conditions can cause this phenomenon, each requiring specific evaluation and management.
Retained Products of Conception (RPOC)
Retained products of conception (RPOC) occur when fetal or placental tissue remains in the uterus after pregnancy loss, delivery, or abortion. This tissue continues to produce HCG, preventing levels from declining. RPOC are more common after earlier miscarriages.
Symptoms include prolonged or heavy vaginal bleeding, abdominal or pelvic pain, and sometimes signs of infection like fever or foul-smelling vaginal discharge. While some RPOC cases may resolve on their own, untreated RPOC can lead to complications such as infection, significant blood loss, or intrauterine adhesions.
Ectopic Pregnancy
An ectopic pregnancy occurs when a fertilized egg implants outside the uterus, usually in a fallopian tube. An early ectopic pregnancy can sometimes be misdiagnosed as a miscarriage, especially if vaginal bleeding and abdominal pain are present. In these cases, HCG levels may not decline or might rise slowly, indicating continued growth of pregnancy tissue in an abnormal location.
Ectopic pregnancies carry a significant risk of fallopian tube rupture as the pregnancy grows, leading to severe internal bleeding. Persistent or slowly rising HCG after a suspected miscarriage requires immediate investigation to rule out an ectopic pregnancy.
Gestational Trophoblastic Disease (GTD) or Molar Pregnancy
Gestational trophoblastic disease (GTD) is a rare group of conditions characterized by the abnormal growth of trophoblastic cells, which normally form the placenta. Molar pregnancy, a type of GTD, results from an abnormality during fertilization where the fertilized egg develops into abnormal tissue instead of a viable fetus. Types include complete molar pregnancy (no embryo) and partial molar pregnancy (some fetal tissue with abnormal placental growth).
These abnormal growths produce HCG, often in high quantities, leading to elevated or rising levels after an apparent miscarriage. While most molar pregnancies are benign, they can develop into a persistent or cancerous form of GTD, known as gestational trophoblastic neoplasia (GTN), requiring close monitoring and treatment.
A New Pregnancy
A new conception is possible if unprotected intercourse occurred, though less common immediately after a miscarriage. HCG levels from a new pregnancy would rise, potentially mistaken for persistent HCG from the previous miscarriage. This possibility emphasizes the need for thorough evaluation and patient history when HCG levels do not decline as expected.
Diagnostic Approaches
When HCG levels remain elevated or rise after a miscarriage, healthcare providers use a systematic approach to determine the cause. This process involves laboratory tests and imaging studies.
Blood tests are fundamental for monitoring HCG levels. Serial HCG measurements, taken over several days, allow observation of the hormone’s trend. A plateau or rise in HCG levels, instead of the expected decline, signals the need for further investigation. These quantitative tests provide precise numerical values, enabling close tracking of HCG dynamics.
Ultrasound imaging, particularly transvaginal ultrasound, is a primary diagnostic tool. It provides detailed views of the uterus, fallopian tubes, and ovaries. Ultrasound can identify retained products of conception, visualize an ectopic pregnancy, or detect the characteristic “snowstorm” or “bunch of grapes” appearance of a molar pregnancy. Doppler ultrasound can also assess blood flow to suspicious tissue, offering additional diagnostic clues.
A comprehensive physical examination and detailed review of the patient’s symptoms are also performed. The provider assesses ongoing bleeding, pain, or other symptoms that might indicate a specific cause. This clinical assessment, combined with lab and imaging findings, helps narrow diagnoses and guide management.
Treatment and Next Steps
Once the cause of persistent or rising HCG is identified, treatment is tailored to the diagnosis. The goal is to resolve the condition, ensure patient safety, and normalize HCG levels.
For retained products of conception (RPOC), treatment options include medical management with medications like misoprostol to help the uterus expel tissue, or surgical procedures such as dilation and curettage (D&C) to remove it. Treatment choice depends on factors like tissue amount, bleeding or infection presence, and patient preference.
Ectopic pregnancies often require medical treatment with methotrexate, a medication that stops cell growth, or surgical intervention, typically via laparoscopy, to remove the ectopic tissue. The decision between medical and surgical management is based on HCG levels, ectopic pregnancy size, and patient clinical stability.
Gestational trophoblastic disease (GTD), including molar pregnancies, is managed by removing the abnormal tissue, usually via D&C. After removal, HCG levels are closely monitored to ensure all abnormal cells are gone and to detect persistent disease. If HCG levels remain elevated or rise, further treatment, often chemotherapy, may be necessary for gestational trophoblastic neoplasia (GTN).
Consistent medical follow-up is paramount, regardless of the diagnosis. This includes continued monitoring of HCG levels until they reach non-pregnant levels and remain stable, especially for GTD. Patients should seek immediate medical attention for severe symptoms like heavy bleeding (soaking through more than two maxi pads per hour for several hours), intense abdominal pain, fever, chills, or signs of infection. These symptoms could indicate a serious complication requiring urgent intervention.