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Molar pregnancy

Molar pregnancy happens when tissue that normally becomes a fetus instead becomes a growth in the uterus – it called a mole. Even though it is not an embryo, a mole triggers symptoms of pregnancy. Molar pregnancy refers to a pregnancy that is a type of gestational trophoblastic disease. It can refer to either a complete or a partial mole.

The frequency of molar pregnancy is about 1/1000 and 1/2000 pregnancies which means that about one out of 1000 – 2000 women with early pregnancy symptoms has a molar pregnancy. Scientists discovered that the frequency of molar pregnancy is higher in Southeast Asia and Mexico.

Molar pregnancy should be treated urgently – the mole tissue can cause serious problems and it should fully and urgently removed.

A molar pregnancy can cause heavy uterine bleeding. Some molar pregnancies lead to gestational trophoblastic disease. Sometimes this disease keeps growing even after the mole is removed.

Molar pregnancy CAUSES

Molar pregnancy

Molar pregnancy

Molar pregnancy is thought to be caused by a problem with the genetic information of an egg or sperm. There are two types of molar pregnancy – complete and partial.

Complete molar pregnancy – when the egg with no genetic information is fertilized by a sperm or when the nucleus of an egg is either lost or inactivated. The sperm grows on its own, duplicates itself because the egg was lacking genetic information but it can only become a lump of tissue. It cannot become a fetus. Usually there is no fetus, no placenta, no fluid and no amniotic membranes. As this tissue grows, it looks a bit like a cluster of grapes. This cluster of tissue is called a mole and it can fulfill the uterus. The uterus is rather filled with the mole that resembles a bunch of grapes. The fluid filled vesicles grow rapidly, which can make the uterus seem larger than it should be for gestational age. Because there is no placenta to receive the blood typically in this cases women will have bleeding into the uterine cavity or vaginal bleeding.
Out of 1000 cases of complete molar pregnancy about 150-200 develop trophoblastic disease that keeps growing after the mole is removed. In few cases trophoblastic disease turns into cancer. Fortunately, almost all women who get this cancer are cured with treatment. In rare cases, the abnormal tissue can spread to other parts of the body.

Partial molar pregnancy – when the egg is fertilized by two sperm. There may be partial placentas, membranes or even a fetus present in a partial mole. However, there are usually genetic problems with the baby. Rarely, a partial mole will exist with twin pregnancy (the other twin rarely survives). Twins are typical for partial molar pregnancy. But in a partial molar pregnancy something goes wrong. The placenta grows into a mole instead. Any fetal tissue that forms is likely to have severe defects.
Out of 1000 cases of partial molar pregnancy, about 50 develop trophoblastic disease.

Sometimes a pregnancy that seems to be twins is found to be one fetus and one mole. But this is very rare.

RISK FACTORS for Molar Pregnancy

There are several factors which can increase the risk of having a molar pregnancy:

  • Age – the risk for complete molar pregnancy steadily increases after 35-40.
  • Early Teens – early sex in adolescents and early pregnancy is a high risk for molar pregnancy.
  • History of molar pregnancy in anamneses – especially if you have had molar pregnancy two or more times.
  • History of miscarriage.
  • Low carotene diet – women who don’t get enough carotene/vitamin A, have a higher rate of complete molar pregnancy.
  • Clomiphene stimulation – infertile women after stimulation of ovulation (with clomipene) have higher risk for molar pregnancy.

Molar pregnancy SYMPTOMS

Symptoms of molar pregnancy are very similar to normal early pregnancy:

  • Missed period;
  • Morning sickness;
  • Severe nausea and vomiting;
  • Vaginal bleeding;
  • Vaginal discharge of tissue that is shaped like grapes (typical for molar pregnancy);
  • Increased level of Human Chorionic Gonadotrophin (hCG);
  • Rapidly growing uterus – uterus that is larger than normal;
  • Hyperthyroidism – including feeling nervous or tired, having a fast or irregular heartbeat, and increased sweating;
  • Absence of fetal movement or heart tone detected;
  • Uncomfortable feeling in the pelvis;
  • Pregnancy induced hypertension prior to 24 weeks;
  • Pulmonary Embolization.
Molar pregnancy

Molar pregnancy

Molar Pregnancy Treatment

Important point is that molar pregnancy should be treated URGENTLY because untreated molar pregnancy can be transformed into trophoblastic disease which can turn into cancer and even can be spread to other parts of the body.

Regular blood tests are important for detecting signs of trophoblastic disease. Serial hCG levels can show a rapid rise in hCG that may indicate that further study is needed. These blood tests should be done over the next 6 to 12 months.

Ultrasound investigations can be useful for determining and monitoring of molar pregnancy development. When doing an ultrasound one sees a “snow storm effect” on the screen.

If the pregnancy has not ended on its own a suction D & C is usually used to evacuate the mole form the uterus. If a woman does not wish to continue with childbearing sometimes a hysterectomy is offered. Induction of labor is not recommended do to increased risks of hemorrhage.

Methotrexate can also be used to help excavate the uterus. (This is an injection that causes the tissues to die and be discharged from the vagina.)

On going treatment includes hCG levels to be taken several times a week, then weekly, until they are “normal” for three weeks. Then you will be tested monthly for six months, and every two months until a total of one year has passed. Pelvic exams should be done too. A rising level of hCG and an enlarging uterus could indicate a choriocarcinoma.

If you do get trophoblastic disease, there’s a small chance that it will turn into cancer. But your doctor will likely find it early so it can be cured with chemotherapy. In the rare case when the cancer has had time to spread to other parts of the body, additional chemotherapy is needed, sometimes combined with radiation treatment.

In case of non-metastatic diseases (not spread to other parts of the body), chances of recovery are nearly 100%. These cases considered as low risk group.

In case of metastatic diseases (spread to other parts of the body, most frequently the liver and the brain), it is considered as the high risk group.

Only 15-30% of women with a molar pregnancy will need further treatment. The main sign that this might be necessary would be continued bleeding after a D & C. Although other signs include abdominal pain, ovarian enlargement, and signs of a metastasis include pulmonary symptoms (coughing, etc.).

Pregnancy should be avoided for the period of one year. Any method of birth control, with the exception of an intrauterine device, is acceptable.

If you are Rh negative, then you will also receive the Rhogam shot.

Future pregnancies after Molar Pregnancy

If you have previously had a molar pregnancy without complications, your risk of having another molar pregnancy is about 1-2%.

It is recommended – couples genetic counseling prior to conceiving again.


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