Gestational trophoblastic disease (GTD) is a group of rare conditions in which abnormal cells grow inside the uterus after conception. Instead of a normal pregnancy developing, the tissue that would normally form the placenta grows out of control. These conditions range from noncancerous molar pregnancies to cancerous forms that can spread to other parts of the body. The good news: even the most serious types are highly treatable, with survival rates approaching 90 to 100%.
How GTD Develops
In a healthy pregnancy, a fertilized egg implants in the uterus and the outer layer of cells (called trophoblasts) begins building the placenta. In GTD, something goes wrong at fertilization, and these trophoblast cells multiply abnormally instead of supporting a developing embryo. The result is a mass of tissue that produces very high levels of hCG, the hormone normally associated with pregnancy. Those elevated hormone levels are what drive many of the symptoms and are also the key marker doctors use to diagnose and monitor the condition.
Types of Gestational Trophoblastic Disease
GTD is divided into two broad categories: molar pregnancies (also called hydatidiform moles), which are noncancerous, and gestational trophoblastic neoplasia (GTN), which includes the cancerous forms.
Complete Molar Pregnancy
A complete mole forms when a sperm fertilizes an egg that has no genetic material of its own. The result contains only paternal DNA. No fetus develops at all. Instead, the placental tissue swells into grape-like clusters of fluid-filled cysts. hCG levels tend to be very high, with nearly half of patients showing levels above 100,000 mIU/mL before treatment. The uterus is often larger than expected for the gestational date, and no fetal heartbeat is present.
Partial Molar Pregnancy
A partial mole occurs when two sperm fertilize the same egg, creating a cell with too many chromosomes. Some fetal tissue may form, but it cannot survive. The presentation is typically less dramatic than a complete mole. hCG levels are lower (fewer than 10% of partial moles reach the 100,000 threshold), the uterus may actually be smaller than expected, and many cases aren’t diagnosed until tissue is examined after what appears to be a miscarriage.
Gestational Trophoblastic Neoplasia
GTN refers to the malignant forms that can develop after a molar pregnancy, a miscarriage, or even a normal pregnancy. These include invasive moles (which grow into the uterine wall), choriocarcinoma (a fast-growing cancer that can spread to the lungs, liver, or brain), and rarer tumors. GTN is diagnosed when hCG levels remain detectable for longer than six months after a molar pregnancy is removed, or when levels rise or plateau instead of declining.
Symptoms to Recognize
The most common symptom of a molar pregnancy is heavy vaginal bleeding early in pregnancy, reported in up to 84% of patients. The blood can be bright red or dark brown, sometimes described as prune juice-like in color. This bleeding happens as the abnormal tissue separates from the uterine lining.
Other early symptoms include severe nausea and vomiting that starts sooner and hits harder than typical morning sickness, driven by the unusually high hCG levels. Some women develop high blood pressure in the first trimester, which is uncommon in normal pregnancies. Later, around 14 to 16 weeks, the excess hCG can trigger symptoms of an overactive thyroid, including a rapid heartbeat and tremors.
For GTN that develops after a molar pregnancy, miscarriage, or delivery, the hallmark symptom is irregular vaginal bleeding that continues or returns when it shouldn’t. Some people have no symptoms at all, and the condition is caught only through routine hCG monitoring.
How GTD Is Diagnosed
Diagnosis usually starts with a blood test measuring hCG levels and a pelvic ultrasound. On ultrasound, a complete molar pregnancy has a distinctive “snowstorm” appearance, created by countless tiny echoes from the swollen placental tissue. The ovaries may also show large cysts (found in up to 40% of cases) caused by the overstimulation from elevated hCG. A partial mole can be harder to spot on imaging and is often confirmed after tissue is sent to a pathology lab.
If GTN is suspected, doctors use a scoring system developed by the International Federation of Gynecology and Obstetrics (FIGO) that considers eight factors, including age, hCG level, tumor size, whether the disease has spread, and how many sites are affected. Each factor receives a score, and the total determines whether the case is classified as low-risk or high-risk. This distinction directly shapes the treatment plan.
Treatment Options
For molar pregnancies, the standard treatment is a procedure called suction evacuation, which removes the abnormal tissue from the uterus. This is typically done under anesthesia and is similar in experience to procedures used for managing miscarriages. Most women recover quickly from the procedure itself.
If the disease progresses to GTN, chemotherapy is needed. Low-risk GTN (FIGO score below 7) is treated with a single chemotherapy drug, most commonly given in cycles over several weeks. Even when the first drug doesn’t fully work and a second agent is added, overall survival approaches 100%. High-risk GTN (score of 7 or higher, or disease that has spread to distant organs) requires a combination of multiple chemotherapy drugs. Some cases also need surgery to remove resistant areas of disease, or radiation therapy for tumors that have reached the brain. Even with high-risk disease, the survival rate is approximately 90%.
Monitoring After Treatment
After a molar pregnancy is removed, regular blood tests tracking hCG levels are essential. The goal is to confirm that hCG drops to undetectable levels and stays there, which signals that no abnormal tissue remains. Current FIGO guidelines recommend monthly hCG monitoring for one month after a partial mole and six months after a complete mole. If hCG is still detectable after six months, or if levels rise at any point, this triggers evaluation for GTN.
For women who have been treated for GTN with chemotherapy, monthly surveillance continues for a year after remission. Most relapses happen during that first year, and since both a relapse and a new pregnancy produce hCG, ongoing monitoring is the only way to tell the difference. About 5.3% of patients treated for GTN experience a relapse overall.
Pregnancy After GTD
Most women who have had GTD can go on to have healthy pregnancies. After a molar pregnancy alone (without chemotherapy), the wait time before trying to conceive depends on how long hCG monitoring continues. After chemotherapy for GTN, doctors typically advise waiting at least 12 months before becoming pregnant. This recommendation exists for two practical reasons: a new pregnancy’s hCG would mask any signs of relapse during the highest-risk window, and there is a theoretical concern about the effects of chemotherapy drugs on eggs.
Research from a large study of 230 women who conceived within 12 months of completing chemotherapy found that their relapse rate was actually about 2 to 2.5%, compared to roughly 5 to 5.6% in women who did not become pregnant during that period. Women who do conceive earlier than recommended can generally be reassured of a favorable outcome, though the standard advice remains to wait.
The risk of having another molar pregnancy in a future conception is estimated at about 1%. A large study of over 5,000 patients found a recurrence rate of 0.7%. While this is higher than the risk for someone with no history of GTD, it remains low.
Who Is at Higher Risk
GTD occurs in roughly 1 to 3 out of every 1,000 pregnancies, though incidence varies significantly by region. Higher rates are reported in parts of Asia, Latin America, Africa, and the Middle East, likely reflecting a combination of genetic factors, nutritional differences, and varying levels of diagnostic surveillance. Age also plays a role: women under 20 and over 35 face a higher risk, and the risk increases further after age 40. A prior molar pregnancy is the strongest individual risk factor for developing another one.