A molar pregnancy — also known as hydatidiform mole — is a noncancerous (benign) tumor that develops in the uterus. A molar pregnancy occurs when the placenta develops into an abnormal mass of cysts rather than becoming a viable pregnancy.
Molar pregnancy is a type of gestational trophoblastic disease (GTD). In a complete molar pregnancy, there's no embryo or normal placental tissue. In a partial molar pregnancy, there's an abnormal embryo and possibly some normal placental tissue. The embryo begins to develop but is malformed and can't survive.
A molar pregnancy can have serious complications — including a rare form of cancer — and requires early treatment. Careful monitoring after a molar pregnancy can help preserve the chance for future healthy pregnancies.
A molar pregnancy may seem like a normal pregnancy at first — but most molar pregnancies cause specific signs and symptoms, including:
If you experience any signs or symptoms of a molar pregnancy, consult your health care provider. He or she may detect other signs of a molar pregnancy, such as:
Image of a molar pregnancy
During a molar pregnancy, the placenta develops into an abnormal mass of cysts. The embryo either doesn't form or is malformed and can't survive. ...
A molar pregnancy is caused by an abnormally fertilized egg. Human cells normally contain 23 pairs of chromosomes. One chromosome in each pair comes from the father, the other from the mother. In a complete molar pregnancy, all of the fertilized egg's chromosomes come from the father. Shortly after fertilization, the chromosomes from the mother's egg are lost or inactivated and the father's chromosomes are duplicated. The egg may have had an inactive nucleus or no nucleus.
In a partial or incomplete molar pregnancy, the mother's chromosomes remain but the father provides two sets of chromosomes. As a result, the embryo has 69 chromosomes, instead of 46. This can happen when the father's chromosomes are duplicated or if two sperm fertilize a single egg.
Up to an estimated 1 in every 1,000 pregnancies is molar. Various factors are associated with molar pregnancy, including:
Tests and diagnosis
If your health care provider suspects a molar pregnancy, he or she may order a blood test to measure the level of human chorionic gonadotropin (HCG) — a pregnancy hormone — in your blood. He or she will also likely do an ultrasound.
With a standard ultrasound, high-frequency sound waves are directed at the tissues in the abdominal and pelvic area. During early pregnancy, however, the uterus and fallopian tubes are closer to the vagina than to the abdominal surface, so the ultrasound may be done through a wand-like device placed in your vagina.
An ultrasound of a complete molar pregnancy may show:
An ultrasound of a partial molar pregnancy may show:
If your health care provider detects a molar pregnancy, he or she will check for other medical problems, including:
After a molar pregnancy has been removed, molar tissue may remain and continue to grow. This is called persistent gestational trophoblastic disease (GTD). It occurs in about 10 percent of women after a molar pregnancy — usually after a complete mole rather than a partial mole. One sign of persistent GTD is an HCG level that remains high after the molar pregnancy has been removed. In some cases, an invasive mole penetrates deep into the middle layer of the uterine wall, which causes vaginal bleeding. Persistent GTD can nearly always be successfully treated, most often with chemotherapy. Another treatment option is removal of the uterus (hysterectomy).
Rarely, a cancerous form of GTD known as choriocarcinoma develops and spreads to other organs. Choriocarcinoma is usually successfully treated with multiple cancer drugs.
Treatments and drugs
A molar pregnancy can't continue as a normal viable pregnancy. To prevent complications, the molar tissue must be removed.
To treat a molar pregnancy, your health care provider will remove the molar tissue from your uterus with a procedure called dilation and curettage (D and C). A D and C is usually done as an outpatient procedure in a hospital.
During the procedure, you'll receive local or general anesthesia and lie on your back with your legs in stirrups. Your health care provider will insert a speculum into your vagina, as in a pelvic exam, to see your cervix. He or she will then dilate your cervix and remove uterine tissue with a vacuum device. A D and C usually takes about 15 to 30 minutes.
If the molar tissue is extensive and there's no desire for future pregnancies, the uterus may be removed (hysterectomy).
After the molar tissue is removed, your health care provider will again measure your HCG level. If you continue to have HCG in your blood, you may need additional treatment. Once treatment for the molar pregnancy is complete, your health care provider will continue to monitor your HCG levels for six months to one year to make sure there's no remaining molar tissue. Because pregnancy makes it difficult to monitor HCG levels, your health care provider may recommend waiting up to one year before trying to become pregnant again.
If you've had a molar pregnancy, talk to your health care provider before conceiving again. He or she may recommend waiting for six months to one year before trying to become pregnant. During any subsequent pregnancies, your health care provider may do early ultrasounds to monitor your condition and offer reassurance of normal development.
Coping and support
Losing a pregnancy is devastating. Give yourself time to grieve. Talk about your feelings and allow yourself to experience them fully. Turn to your partner, family and friends for support. If you're having trouble handling your emotions, consult your health care provider or a counselor.
Last Updated: 2010-06-18
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