Molar Pregnancy

When a pregnancy test returns with a positive result it usually means a baby will be born in the next 9 months or so. However there are complications that can occur in any stage of pregnancy. In the first few months of a pregnancy bleeding or pain can signify a problem with the developing embryo. Sometimes this occurs in a normal pregnancy but it may signify a pending miscarriage, ectopic pregnancy or less commonly a molar pregnancy. Molar pregnancy is part of a spectrum of diseases called gestational trophoblastic disease.

Gestational trophoblastic disease includes complete molar pregnancies, partial molar pregnancies, invasive mole and choriocarcinoma. Complete molar pregnancies consist entirely of placental tissue. A fetus is not present. It is thought that they develop from fertilization by a sperm of an egg that does not have any genetic material. Thus the tissue develops from the chromosomes of 2 separate sperm or duplication of the chromosomes of a single sperm. A partial mole does contain a fetus as well as abnormal placental tissue but the fetus usually has a chromosomal complement called triploidy (3 copies of chromosomes rather than the normal 2 copies) and cannot survive. Invasive moles have the ability to spread into the uterine wall or even adjacent structures such as the vagina. Choriocarcinoma is a cancer composed of placental type tissue; it can follow a normal or abnormal pregnancy. Choriocarcinoma is an extremely aggressive cancer that has the ability to spread anywhere in the body. Fortunately it is quite rare, and treatable with chemotherapy if appropriately diagnosed.

Molar pregnancies occur in 1 out of every 1000 pregnancies in the United States. They are more common in women over the age of 40 and in women with a prior history of a molar pregnancy. Symptoms are varied; the most common presentation is bleeding in the first trimester. An ultrasound will show characteristic findings of a molar pregnancy, the uterus looks like it is filled with a "cluster of grapes" or what is called a "snowstorm" appearance. A fetus is not present in a complete mole. Partial moles will have a fetus present and the placental tissue has a more varied appearance. With a molar pregnancy the levels of human chorionic gonadotropin (HCG) are abnormally high. Thus the women will feel pregnant and may have exaggerated pregnancy symptoms. Some women will have severe nausea and vomiting. Sometimes large cysts on the ovaries may develop. Rarely thyroid disease or preeclampsia ( a type of high blood pressure unique to pregnancy) may develop.

Once the diagnosis of a molar pregnancy has been established a D and C is performed to evacuate the uterus. This is done under anesthesia in an operating room. After the procedure is completed the patient must have blood drawn weekly to determine the levels of HCG. These will gradually return to non-pregnant levels. Because of the risk of persistent trophoblastic disease the levels of HCG are periodically checked for a full year after the D and C. If they do not fall then a persistent mole is diagnosed. This occurs in about 20% of molar pregnancies and even less often with partial molar pregnancies. Persistent trophoblastic disease means that there are still abnormal cells present in the uterus or elsewhere. This is treated with chemotherapy to prevent spread of the disease to other organs.

There are rare cases where women will have a persistent positive pregnancy test when her blood is tested but does not have gestational trophoblastic disease. These women have another substance in their blood that gives a false positive result with a blood pregnancy test. This substance is not present in urine so a urine pregnancy test can help distinguish between a true positive HCG level versus a false positive.

Women who have had a molar pregnancy should wait at least 6 months before attempting pregnancy. This can be very frustrating to women who want to become pregnant. However because of the risk of persistent mole it is important to avoid confusion and treatment dilemmas regarding rising HCG levels; that is: are they from a persistent molar pregnancy or a normal pregnancy? Oral contraceptives are safe to use after a molar pregnancy.

Although an unusual complication of pregnancy molar pregnancies can be easily diagnosed and treated in the majority of cases. Unusual bleeding or severe early pregnancy symptoms should be reported to your physician, as they can be a sign of an abnormal pregnancy.