Hydatidiform mole is also called molar pregnancy. This is a rare complication, occuring in approximately 1 in 1,000 pregnancies in the United States and Europe. It is more frequent in parts of Asia. In this condition, the chorionic villi of pregnancy are converted into a mass of grapelike cysts. In a complete mole, there is no embryonic or fetal tissue. In a partial mole, there will be fetal tissue. On an extremely rare occasion, a twin pregnancy may result in one viable fetus and one mole. Such pregnancies have gone to term with the birth of a normal baby, but this is extraordinarily rare.

Hydatidiform mole is most frequent in women at either end of the childbearing years young adolescents and women over the age of 45. There is a ten times higher chance of having a molar pregnancy if you get pregnant at age 45 than there is if you get pregnant at a younger age. Molar pregnancies have been seen in women at the age of 50, whereas a normal pregnancy at that age is practically unknown, except with as sisted reproductive technologies. Molar pregnancy recurs about 1 to 2 percent of the time.
Signs of a molar pregnancy include persistent nausea and vomiting, bleeding occurring at about the twelfth week of pregnancy or earlier, a uterus larger than expected for the dates of the pregnancy, and absence of a fetal heartbeat or fetal activity, even though the uterine size suggests that the fetal heart should be heard and the woman should feel movement. A characteristic sign of a molar pregnancy is the development of pregnancy induced hypertension or preeclampsia in the first half of pregnancy. This is ordinarily a condition of the second half of pregnancy, usually not occurring before 24 weeks gestation.

When a woman presents with these symptoms, a blood test for human chorionic gonadotropin (hCG) is ordered along with a sonogram. The hCG levels will be unusually high in the presence of a molar pregnancy. Ultrasound identifies the characteristic grapelike mass quite accurately.

The treatment for hydatidiform mole is termination of the pregnancy. As this is a pregnancy loss, consider seeking support and counseling. Although hydatidiform mole is not a life-threatening condition, in about 20 percent of cases it can progress to a malignant tumor. This is called a gestational trophoblastic tumor. One type of tumor is a rapidly growing malignancy called choriocarcinoma.

All women with a molar pregnancy should be evaluated after the pregnancy for evidence of a gestational trophoblastic tumor. The followup visit consists of measuring hCG levels in the blood at frequent intervals until they return to normal. Right after termination, hCG is measured at 2-week intervals. Once the levels are undetectable, which usually occurs within 3 months, they can be measured every month for 6 months and then every other month for a complete year. Pregnancy should be avoided until at least a year has elapsed without elevated hCG in blood. If the hCG levels do not regress, or if they rise after the molar pregnancy has been terminated, then further treatment is required.

Signs of disease spread should be looked for. A chest X ray is done, for example. If further childbearing is not desired, treatment may consist of a hysterectomy. If the woman wishes to preserve her reproductive capability, then chemotherapy is the treatment of choice. Chemotherapy may be needed following hysterectomy if the disease has spread. Whenever possible, gestational trophoblastic tumors should be treated by specialists experienced in their care.