What Is Gestational Trophoblastic Disease?
Gestational trophoblastic disease (GTD) is a rare group of interrelated tumors that develop after conception and lead to abnormal development of the placenta. More than 80 percent of GTD cases are non-cancerous. All forms of GTD can be treated, and in the great majority of cases, cured. Most women who have had a single incidence of GTD can go on to have normal subsequent pregnancies.
There are three main types of GTD:
Hydatidiform Mole, or Molar Pregnancy
A hydatidiform mole, also called a molar pregnancy, is a form of gestational trophoblastic disease that arises when fertilization of an egg results in an abnormal pregnancy. With a molar pregnancy, the fetus is never viable.
There are two types of molar pregnancies, complete and partial. A complete molar pregnancy develops when the fertilized egg lacks maternal genes. The pregnancy that results contains no fetal tissue and resembles grape-like cysts that fill the uterine cavity. A partial molar pregnancy occurs when more than one sperm fertilizes a normal egg and results in a pregnancy in which both the fetus and placenta are abnormal. The term partial is used because the placenta contains both normal tissue and grape-like cysts similar to that seen in complete moles.
Eighty percent of molar pregnancies are benign in that they cause no further trouble after they are removed from the uterus. However, in approximately 20 percent of complete molar pregnancies and 1-4 percent of partial moles, the molar tissue either spreads locally within the muscular wall of the uterus (called invasive mole) or spreads more widely to other parts of the body, most commonly the lungs (called metastases), requiring treatment. Hydatidiform moles occur in only one of every 1,000-1,200 pregnancies in the United States.
Choriocarcinoma is a highly malignant form of GTD that spreads rapidly throughout the body and requires vigorous treatment. It may have begun as a molar pregnancy or from tissue that remains in the uterus following a miscarriage or childbirth. Choriocarcinoma is even less common, arising in only one of every 20,000-40,000 pregnancies.
Placental-Site and Epithelioid Trophoblastic Tumors
Placental-site and epithelioid trophoblastic tumors, are very rare forms of the disease that arises in the uterus at the site where the placenta was attached. These tumors penetrate the muscle layer of the uterus and usually do not spread to other parts of the body.
Risk Factors for GTD
Although doctors cannot always explain why a woman develops GTD, there are a number of factors that may increase a woman's risk of developing the disease:
- Age: Since GTD develops from pregnancy, this disease only occurs in women in the childbearing age group. The risk of developing GTD is higher in women over the age of 40, and in very young women and teens.
- Prior GTD: Women who have had a previous molar pregnancy or choriocarcinoma are at increased risk. For example, a second molar pregnancy occurs 10 times more frequently than the first mole.
- Diet: Women whose diets are low in beta carotene or vitamin A appear to have a higher risk of developing complete molar pregnancy.
- Fertility problems: Women who have had miscarriages appear to have an increased risk of complete and partial molar pregnancy.
The most common symptoms of hydatidiform mole are feeling pregnant and vaginal bleeding, which can be either bright red or watery brown discharge. Other symptoms include:
- Abdominal bloating
- Nausea and vomiting, which is generally more severe than in normal pregnancy
- Fatigue, shortness of breath, and lack of energy due to anemia, if there has been a great deal of blood loss
- Signs of an overactive thyroid gland, including rapid heartbeat, warm skin, and mild shaking
- High blood pressure due to pre-eclampsia (also called toxemia of pregnancy) which can develop if the molar pregnancy continues beyond 12 weeks
Women who develop choriocarcinoma may be symptom-free or experience symptoms based on which organ(s) is (are) involved:
- Uterus or vagina: Vaginal bleeding, discharge
- Lung: Coughing up blood, shortness of breath, chest pain
- Liver: Abdominal pain
- Brain: Headache, trouble with vision, weakness or loss of function, convulsion
- Kidney: Blood in urine
- Bowel: Blood in stool
Learn more about GTD from the International Society for the Study of Trophoblastic Diseases.