Human Chorionic Gonadotropin (hCG) is the hormone produced by the trophoblast cells of the developing placenta, serving as the primary biochemical marker of pregnancy. Following a miscarriage, the body is expected to clear this hormone, with levels typically dropping by around 50% every 24 to 48 hours in the initial days. Normalization, meaning the return to non-pregnant levels, generally occurs within four to six weeks, depending on the initial hormone concentration. When the hCG level plateaus, declines too slowly, or begins to rise again after a confirmed pregnancy loss, it is a significant medical finding that requires immediate and specific investigation.
Retained Products of Conception
The most frequent reason for a persistent or slowly rising hCG level after a miscarriage is the presence of Retained Products of Conception (RPOC). This refers to placental or fetal tissue that was not fully expelled from the uterus during the miscarriage process. The remaining tissue consists of metabolically active trophoblast cells, which produce the hCG hormone.
Because this tissue is still viable, the hCG level does not follow the expected rapid decline but instead shows a plateau or a slow, incomplete drop. In some cases, if the remaining tissue proliferates slightly, a slow rise in the hormone level may be observed. The clinical picture often includes continued irregular or heavy vaginal bleeding, sometimes accompanied by pelvic pain.
RPOC is a diagnosis of exclusion, meaning other causes must be ruled out, but it is often suspected based on the hCG pattern and ultrasound findings. A decline of less than 21% at two days or less than 60% at seven days after the miscarriage event is strongly suggestive of retained tissue. While the hCG level is an important indicator, definitive diagnosis relies on visualization of the retained tissue within the uterine cavity.
Gestational Trophoblastic Disease (GTD)
A rarer cause for a rising hCG level is Gestational Trophoblastic Disease (GTD), a group of conditions arising from the trophoblast, the tissue that forms the placenta. These conditions include hydatidiform mole (molar pregnancy), invasive mole, and choriocarcinoma. The pathology involves the abnormal growth and proliferation of these trophoblast cells, which continue producing hCG.
In a complete hydatidiform mole, the placental tissue develops abnormally into a mass of cysts, but no fetus is present. Trophoblastic proliferation is often extensive, leading to very high and rapidly rising hCG levels, frequently exceeding 100,000 mIU/mL. A partial hydatidiform mole involves a more limited proliferation and may present with less dramatic hCG levels, often mimicking a typical miscarriage or RPOC.
The rapid rise in hCG is a distinct characteristic of GTD, differentiating it from the slow plateau seen with RPOC. GTD requires specialized treatment because the abnormal tissue, particularly choriocarcinoma, can become locally invasive or spread to other parts of the body.
Diagnostic Procedures for Rising hCG
The first step in investigating a concerning hCG pattern is serial quantitative blood testing to monitor the hormone’s trajectory. Providers look for two consecutive rises of 10% or more over a two-week period or a prolonged plateau to confirm the need for further investigation. This serial testing establishes a clear biochemical pattern, which helps distinguish between the slow rise of RPOC and the rapid rise of GTD.
A transvaginal ultrasound is the next step, offering a visual assessment of the uterine cavity. For RPOC, the ultrasound may show an echogenic (bright) mass or a thickened endometrium, sometimes with increased blood flow detected by Doppler imaging. In contrast, a molar pregnancy presents a characteristic “snowstorm” appearance due to the cystic, edematous villi, often accompanied by ovarian cysts.
If tissue is surgically removed, a pathology examination is mandatory to provide a definitive diagnosis. This analysis confirms the presence of chorionic villi (indicating RPOC) or the specific features of molar tissue (confirming GTD). The combination of the hCG trend, the ultrasound image, and the tissue pathology report guides the subsequent management plan.
Medical Management and Next Steps
Treatment for Retained Products of Conception is determined by the patient’s symptoms and tissue volume. If the patient is stable and tissue volume is small, expectant management (waiting for natural passage) or medical management using misoprostol may be used to prompt uterine contractions. Surgical intervention, typically a suction Dilation and Curettage (D&C) or hysteroscopy, is reserved for cases with heavy bleeding, signs of infection, or failure of conservative methods.
Management of Gestational Trophoblastic Disease begins with surgical evacuation, usually a suction D&C, to remove the abnormal tissue. Following evacuation, patients enter a surveillance period where weekly hCG levels are monitored until they normalize and remain undetectable for a specified duration (often six months to a year). If the hCG levels plateau or rise after the initial evacuation, it indicates persistent or invasive GTD, which requires specialized oncologic care, often involving chemotherapy.
Patients are advised to postpone future pregnancy attempts until the hCG surveillance period is complete, particularly after a molar pregnancy, ensuring the hormone level is a true reflection of the disease status. This monitoring period detects any recurrence early, ensuring the best outcome for the patient’s long-term health.