Gestational trophoblastic disease (GTD) is a rare group of cancers in women that can occur during pregnancy. It develops in the uterus when cancerous cells grow in the tissues that are formed following conception (the union of a sperm and egg), and it usually becomes evident some ten to 16 weeks after conception. Examination of GTD tissue has shown that the tumor often develops from an abnormal number of chromosomes when the sperm and egg unite. GTD tissue can also arise from abnormal development of the placenta.
More than 80 percent of GTD cases are noncancerous. All forms of GTD can be treated, and in the great majority of cases the treatment results in a cure. Most women who have had a single incidence of GTD can go on to have normal pregnancies.
Types of GTD
There are three main types of GTD:
A hydatidiform mole (also called a “molar pregnancy”) is a form of GTD that arises when the sperm and egg join but do not develop into a fetus, forming a tissue that resembles grape-like cysts. Hydatidiform moles may be complete (containing no fetal tissue) or partial (containing some embryonic or fetal tissue). These tumors rarely spread beyond the uterus to other parts of the body; a small percentage of them may develop into cancerous GTD.
Chorioadenoma & Choriocarcinoma
Chorioadenoma and choriocarcinoma are cancerous forms of GTD. Chorioadenoma spreads locally within the muscular wall of the uterus; choriocarcinoma spreads more widely within the body. These types of GTD may have begun as a hydatidiform mole or from tissue that remains in the uterus following a miscarriage or childbirth.
Placental-site GTD is a very rare form of the disease that arises in the uterus at the site where the placenta was attached. These tumors usually do not spread to other parts of the body, but they can sometimes penetrate the muscle layer of the uterus.
Hydatidiform moles occur in only one of every 1,500 pregnancies in the United States. Choriocarcinomas are even less common, arising in only one of every 20,000 to 40,000 pregnancies. When GTD does occur, it is most commonly found in very young women (under age 17) and in women who are in their 30s and 40s.
Although doctors cannot always explain why a woman developed GTD, the following factors may increase the risk of developing this disease:
- Age Because a woman’s egg must be fertilized with sperm before GTD can occur, women of childbearing age are at greater risk than women who have reached menopause and are no longer producing eggs. The risk of GTD, although always low, is highest in women who become pregnant younger than age 20 or over the age of 40.
- Prior GTD Women who have had one hydatidiform mole or choriocarcinoma are at increased risk of having another.
- First Pregnancies Women who have not had children previously may be more likely to develop GTD than those who have had several children.
- Blood Type For unexplained reasons, women with blood types B or AB have a slightly higher risk of GTD than those with types A or O. However, this risk factor is not as strong as age and past history of GTD.
- Diet There is some evidence that indicates that women whose diets are low in beta carotene or vitamin A may have a slightly higher risk of developing GTD.
- Use of Oral Contraceptives Women taking birth control pills are 50 percent more likely to develop GTD when pregnancy occurs. Though the vast majority of women using oral contraceptives do not develop GTD, the risk is higher for women using oral contraceptives for a longer period of time.
Most women with GTD feel pregnant, then develop vaginal bleeding. In addition to abdominal swelling, other symptoms may include:
- nausea and vomiting that may be more frequent and severe than that which occurs during a normal pregnancy
- irregular, nonmenstrual vaginal bleeding, and blood clots or a watery brown discharge that pass from the vagina
- fatigue, shortness of breath, and lack of energy due to anemia, which may develop as a result of increased blood loss
- rapid heartbeat, warm skin, and mild tremor or shaking due to an overactive thyroid gland, which occurs in about 7 percent of women with complete hydatidiform moles
- preeclampsia or toxemia, which are toxic conditions that cause a sharp rise in a woman’s blood pressure, usually during the third trimester but sometimes earlier
- lack of fetal movement and fetal heart sounds