Hydatidiform mole
A hydatidiform mole, also referred to as a molar pregnancy, is a uterine growth that occurs during early pregnancy, resulting from an abnormally fertilized egg. There are two types: complete and partial. A complete mole has no embryonic tissue and arises from an egg with no nucleus, while a partial mole may contain some embryonic tissue. Symptoms often include irregular dark brown or red vaginal bleeding, nausea, and abdominal pressure. Diagnosis usually occurs via ultrasound during the first trimester, and treatment typically involves a surgical procedure called dilation and curettage (D&C) to remove the abnormal tissue. While the incidence of hydatidiform moles varies globally, it is about 1 in 1,500 pregnancies in the U.S., with higher rates reported in East and Southeast Asia. Follow-up care is essential, as levels of the hormone human chorionic gonadotropin (HCG) are monitored to ensure no residual molar tissue remains. If left untreated, a hydatidiform mole can lead to serious complications, including cancer in rare cases. Understanding this condition is vital for affected individuals and their healthcare providers to ensure appropriate management and care.
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Hydatidiform mole
ALSO KNOWN AS: Molar pregnancy, gestational trophoblastic disease
RELATED CONDITIONS: Choriocarcinoma
DEFINITION: A hydatidiform mole is a uterine growth during early pregnancy. About 10 to 20 percent of complete hydatidiform moles and 5 to 10 percent of partial moles develop into an invasive mole, sometimes called chorioadenoma destruens. In comparison, 3 percent of complete moles form a choriocarcinoma, a rare type of uterine cancer. Partial moles rarely develop into choriocarcinoma. These growths, including the mole, are classified as gestational trophoblastic tumors.
Risk factors: Pregnancy before age fifteen or after age forty increases the risk for a hydatidiform mole. A prior miscarriage or a previous hydatidiform mole slightly increases the risk. More than one previous hydatidiform mole significantly raises the chances of a future one. Around one of every hundred women who experienced a previous molar pregnancy will have another.
Etiology and the disease process: A hydatidiform mole arises from an abnormally fertilized egg. The early placental tissue grows into a mass containing cysts resembling a cluster of grapes called trophoblasts. There is usually no embryo present. However, in rare cases, a fetus and a partial hydatidiform mole develop together. Such cases typically lead to fetal death and miscarriage.
There are two types of hydatidiform moles—complete and partial. A complete mole is formed from an ovum with no nucleus or embryonic tissue. A partial mole develops from an ovum that still has its nucleus and often contains embryonic tissue.
A hydatidiform mole is a form of gestational trophoblastic disease (GTD). If the abnormal tissue grows after treatment, it is considered persistent GTD. An invasive mole is the most common form of persistent GTD, but choriocarcinoma may develop in rare cases.
Incidence: Reported incidence varies widely in different countries and regions. In the United States, a hydatidiform mole occurs in about 1 in 1,500 pregnancies. The rate is much higher in East and Southeast Asia.
Symptoms: The most common symptom is irregular dark brown or red vaginal bleeding during the first three months of pregnancy. Other symptoms may include lack of menstruation, nausea, vomiting, pain or pressure in the lower abdomen, and signs of hyperthyroidism, such as a rapid heartbeat, sweating, and tremor. Most molar pregnancies are found in the first three months. Still, if it continues, the woman may have a larger-than-normal uterus and signs of preeclampsia, including high blood pressure, protein in the urine, ovarian cysts, and swelling of the lower legs and feet.
Screening and diagnosis: Ultrasound allows most moles to be diagnosed in the first trimester before symptoms develop. The diagnosis is confirmed after the suspected tissue is removed and examined under a microscope. A blood test that shows higher-than-normal levels of human chorionic gonadotropin (HCG) may indicate a complete mole. Other signs include no embryo, fetus, amniotic fluid, or the presence of ovarian cysts or a thick, cystic placenta.
Treatment and therapy: A hydatidiform mole is a medical emergency. Treatment involves dilation and curettage (D&C), a surgical procedure that gently scrapes the lining of the uterus to remove all molar tissue, including a developing embryo, if present. Levels of HCG are checked for up to a year after surgery to make sure no molar tissue remains. If a woman has an HCG level of zero after surgery, no further treatment is needed.
Prognosis, prevention, and outcomes: There is no known prevention method. Women who have had a hydatidiform mole should avoid pregnancy during the follow-up period, which may last anywhere from six months to two years after HCG levels return to zero, as pregnancy will interfere with HCG monitoring. Untreated, a hydatidiform mole can cause significant bleeding and, in some cases, may progress to cancer. Persistent gestational trophoblastic neoplasia (GTN) may occur following complete molar pregnancies, characterized by the continued growth of molar tissue. If GTN develops into choriocarcinoma, a rare cancer that spreads to other organs, chemotherapy is required.
Bibliography
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