What Is A Molar Pregnancy: Causes, Symptoms And Treatment

What Is A Molar Pregnancy: Causes, Symptoms And Treatment

With a molar pregnancy, because of a genetic error during the fertilisation process, tissue in the uterus becomes an abnormal mass or tumor instead of a placenta. Read more here...

A molar pregnancy happens when something goes wrong in the early stages of fertilisation because of which, the baby and placenta don’t develop properly. Due to this, the pregnancy ends in a loss.

What is a molar pregnancy?

A molar pregnancy is when a foetus does not form properly in the womb and a baby doesn’t develop. A lump of abnormal cells grows in the womb instead of a healthy foetus.

During a healthy pregnancy, the placenta grows inside your uterus. It nourishes your baby through the umbilical cord. With a molar pregnancy, because of a genetic error during the fertilisation process, tissue in the uterus becomes an abnormal mass or tumor instead of a placenta.

This tissue looks like a large collection of grape-like cell clusters, and its growth is rapid compared to normal foetal growth.

what is a molar pregnancy


Molar pregnancies rarely involve a developing embryo. They are rare, occurring in 1 out of every 1,000 pregnancies. Molar pregnancies are also called gestational trophoblastic disease (GTD), hydatidiform mole or simply referred to as a “mole.”

Types of molar pregnancy

There are two types of molar pregnancies, “complete,” and “partial”.

Complete molar pregnancy

In complete molar pregnancies, there is only a placenta and no foetus. It happens when the sperm fertilises an empty egg. Because the egg is empty, no baby is formed. 

The placenta grows and produces the pregnancy hormone, hCG. An ultrasound will show that there is no foetus, only a placenta.

Partial molar pregnancy

Partial molar pregnancy happens when the mass contains both the abnormal cells and an embryo that has severe birth defects. The abnormal foetus can’t survive or develop into a baby.

An extremely rare version of a partial molar pregnancy is when twins are conceived but one embryo begins to develop normally while the other is a mole.

In these cases, the healthy embryo will very quickly be consumed by the abnormal growth.

what is a molar pregnancy


Causes of molar pregnancy

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, an empty egg is fertilized by sperm, and all of the genetic material is from the father. The egg contains only the chromosomes from the father and no chromosomes from the mother at all. This means that there is no baby.

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. It will be genetically abnormal and unable to live beyond 3 months.

Symptoms of molar pregnancy

A molar pregnancy may only be spotted during a routine ultrasound scan at 8-14 weeks or found out during tests carried out after a miscarriage.

Here are some signs and symptoms:

  • Vaginal spotting or bleeding, or a dark discharge from the vagina in early pregnancy (usually in the first three months) – this may contain small, grape-like lumps
  • Nausea and vomiting
  • An unusually swollen tummy
  • Rapid uterine growth — the uterus is too large for the stage of pregnancy
  • Pelvic pressure or pain
  • Overactive thyroid (hyperthyroidism)
  • Early preeclampsia (high blood pressure)
  • Increased hCG levels
  • No foetal movement or heart tone detected
  • Ovarian cysts
  • Anaemia

Some of these symptoms are quite common in pregnancy and are not necessarily a sign that anything is wrong with your baby.

Who is at risk of molar pregnancy

  • Teenage girls and women over the age of 40
  • Women with a history of miscarriage
  • Previous molar pregnancy – if you’ve had a molar pregnancy before, your chance of having another one is about 1 in 80, compared with 1 in 600 for women who haven’t had one before. If you’ve had two or more molar pregnancies, your risk of having another is around 1 in 5.
  • Ethnicity – Mexico, Southeast Asia, and the Philippines have higher rates than the US for molar pregnancies. In the US, approximately 1 out of 1,000 pregnancies is a molar pregnancy. White women in the US are at higher risk than black women.

How is a molar pregnancy treated

If an ultrasound scan shows that you have a molar pregnancy, treatment to remove it will be recommended.

Three main treatments can be used:

  • Suction removal

The abnormal cells are sucked out using a thin tube passed into your womb through your vagina. This is usually done under general anaesthetic.

The procedure is sometimes called SMM (Surgical Management of Miscarriage) or D&C (Dilatation and Curettage) or ERPC (Evacuation of Retained Products of Conception.)

  • Medication

If the growth is too large to be sucked out, you may be given medication to make it pass out of your vagina.

  • Surgery to remove the womb (hysterectomy)

This may be an option if you don’t want to have any more children in the future.

Speak to your doctor about the benefits and risks of the different options. Most women are successfully treated with suction removal and can go home later the same day.

Approximately 90% of women who have a mole removed require no further treatment. Follow-up procedures (regular blood or urine tests) that monitor the hCG levels can occur monthly for six months.

Sometimes, abnormal cells may be left in your womb after treatment. These usually go away on their own within a few months, but further treatment may sometimes be needed to remove them.

In a few cases, abnormal cells left in the womb after treatment don’t go away on their own. This is called persistent trophoblastic disease (PTD). PTD can be serious because the abnormal cells can regrow or spread to other parts of the body, similar to cancer, if it’s not treated.

Treatment involves taking medication to kill the abnormal cells (chemotherapy) for a few months. Another treatment option is removal of the uterus (hysterectomy).

How you may feel about a molar pregnancy physically and  emotionally

A positive pregnancy test offers much joy and hope to the mum. But a molar pregnancy always ends in a loss. It might take time to recover emotionally from this.

what is a molar pregnancy

Mums should talk to their partner, family or friends about how they feel. They can also consider counselling and joining online support groups.

They should stick with their follow-up appointments to make sure that all the abnormal cells have been removed.

Remember that a molar pregnancy does not impact your fertility. Most women with successfully treated molar pregnancies subsequently go on to conceive healthy babies without any problems.

It is okay to have sex as soon as you feel physically and emotionally ready. If you have any bleeding after your treatment though, don’t have sex until this stops.

It is recommended not to try for a baby until one year after a molar pregnancy. Use contraception (other than intrauterine device) until it’s safe to get pregnant again.

Genetic counselling prior to conceiving again is helpful for some couples.

Can I still get pregnant after a molar pregnancy?

Yes, it is still possible to get pregnant after a molar pregnancy. Having a molar pregnancy doesn’t affect your chances of getting pregnant again, and the risk of having another molar pregnancy is small (about 1 in 80).

It’s best not to try for a baby though, until your after-treatment monitoring has finished, in case you need further treatment to remove any cells left in your womb. Pregnancy is best avoided for one year after a molar pregnancy.

Use contraception until your doctors say it’s safe to get pregnant again. You can use any method of birth control except intrauterine implants, which should only be used once your hCG level has returned to normal.

Will I have another molar pregnancy?

If you’ve had a molar pregnancy before, your chance of having another one is about 1 in 80. If you’ve had two or more molar pregnancies, your risk of having another is around 1 in 5.

Prevention tips

If you’ve had a molar pregnancy, talk to your doctor before conceiving again. Your doctor may recommend waiting for one year before trying to become pregnant. The risk of recurrence is low, but higher than the risk for women with no previous history of molar pregnancy.

During any subsequent pregnancies, your doctor may do early ultrasounds to monitor your condition. He or she may also discuss prenatal genetic testing, which can be used to diagnose a molar pregnancy.

(Source: American Pregnancy Association, NHS, MayoClinic, WebMD Featured Image: Wikipedia)

Also READ: What is vanishing twin syndrome: Causes, symptoms and diagnosis

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