Molar pregnancy: what it is, symptoms, diagnosis and treatment

Have you recently been diagnosed with a molar pregnancy or are you worried that you may have one? Molar pregnancies are rare in Europe and occur in only about one in 1000 pregnancies and are responsible for about one in 141 abortions. However, it can be a real shock to receive the diagnosis of a molar pregnancy, so it is perfectly normal if you feel very upset. It is important to know that molar pregnancies are not caused by something you did or did not do and therefore, you do not have to feel ‘guilty’ in the first place. Then what you can do is try to better understand what it is, so as to be more informed and prepared when you talk about it with your doctor or health professional.

What is a molar pregnancy

Molar pregnancies are not normal pregnancies, cannot survive and never lead to the birth of a child.

Things go wrong when the egg is normally fertilized and then implants in the wall of the uterus – as it would in a normal pregnancy – but the contents of the egg do not lead to the development of a normal embryo.

Molar pregnancies are a benign disease of the trophoblast . Trophoblasts are the cells that become the placenta in a normal pregnancy. In a molar pregnancy, trophoblast cells multiply rapidly and grow out of control. The term mola simply indicates a growth; of fabric.

A molar pregnancy is characterized by the presence of a hydatidiform mole (or hydatid mole, hydatidosa mole), with the word mole used to simply denote a tuft of tissue.

Types of molar pregnancies

Molar pregnancies are divided into partial and complete.

Complete molar pregnancies occur when one sperm (or sometimes two sperm) fertilizes an empty egg. The genetic material is all that of sperm. No fetal tissue can develop.

In partial molar graivdances two spermatozoa fertilize an egg. Because there is male and female genetic material, there is usually evidence of a fetus or fetal red blood cells.

In both complete and partial moles there is an overgrowth of trophoblastic cells.

Symptoms of molar pregnancy

Not necessarily a molar pregnancy is accompanied by symptoms. This means you may not know you have one until you are diagnosed.

Some women show up for their first ultrasound, around the 12th week of pregnancy, and discover, on the monitor, that, instead of having a fetus in her womb in its expected stage of development, there is only a mass of cells classic of a molar pregnancy.

Similarly, women who have had a miscarriage treated in the hospital may find out that they have had a molar pregnancy only after the tissue that has been removed from their body is examined.

However, there are some symptoms that could potentially indicate a molar pregnancy. If you’ve had a positive pregnancy test result and are experiencing any of the following problems, you should talk to your doctor:

  • Irregular vaginal bleeding with darker blood than normal and with some small grape-like cysts in the blood.
  • hyperemesis, i.e. excessive vomiting and nausea.
  • excessive uterine enlargement. If your baby bump looks much larger than it should for the stage of pregnancy you’re in, it could be a sign of the rapid multiplication of molar pregnancy cells.
  • persistent vaginal bleeding (meaning it lasts longer than expected) after a miscarriage or termination of pregnancy.

Causes of molar pregnancy

The causes of molar pregnancy are unknown. There is nothing that leads them back to the wrong behavior of the woman, just as there is nothing she could have done to avoid them.

As we have seen above, they are rare diseases.

It seems that there are some women who have a higher risk of a molar pregnancy than others, these are:

  • Teenage girls
  • women over 45
  • Women of Asian descent
  • women who have had a previous molar pregnancy

Diagnosis of molar pregnancy

Doctors diagnose molar pregnancy with:

  • a blood test. hCG (human chorionic gonadotropin), also known as the pregnancy hormone, increases its concentration in the blood, gradually during pregnancy. HCG is produced by trophoblastic cells. In a molar pregnancy trophoblastic cells are multiplying rapidly, so the level of hCG increases rapidly and is usually much higher than would be expected in a normal pregnancy. It’s the high levels of hCG that can make you feel sick with nausea and vomiting.
  • an ultrasound. An ultrasound gives a clear picture of the size and characteristics of pregnancy to determine if they respond with those of a molar pregnancy.
  • histological examination (biopsy) – To give a definitive diagnosis of molar pregnancy it is necessary to examine the tissues under a microscope (histology). Eventually these will show the characteristic changes that confirm the diagnosis.

Treatment of molar pregnancy

Very often molar pregnancies end in miscarriage and tissues are naturally expelled with vaginal bleeding.

If this does not happen, they can be surgically removed with a procedure performed under anesthesia through which the tissues of pregnancy are extracted through the vagina.

After treatment, your doctor will check your blood and urine tests for several weeks to make sure your hCG levels have returned to normal. This is a good indication that all molar tissue has been eliminated.

If the mole persists or has spread but is considered low risk, chemotherapy is required, which may include only one drug (methotrexate or dactinomycin).

Getting pregnant after a molar pregnancy

It is important that treatment and follow-up after a molar pregnancy is complete before attempting another pregnancy.

If you’ve had chemotherapy treatment for your molar pregnancy, you need to wait 12 months after it’s over before trying to get pregnant again.

Although molar pregnancies are more common in women who have already had one, it is reassuring to know that molar pregnancies do not affect fertility.

Katherine Johnson, M.D., is a board-certified obstetrician-gynecologist with clinical expertise in general obstetrics and gynecology, family planning, women’s health, and gynecology.

She is affiliated with the Obstetrics and Gynecology division at an undisclosed healthcare institution and the online platform,

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