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. When a tumour develops in the uterus, the placenta swells into a mass of cyst-like sacs filled with fluid. Molar pregnancies make up for 1 in 1,000 pregnancies (0.1%).

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 tumour 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


The placenta normally isn’t able to support or grow a baby at all, therefore this type of pregnancy doesn’t last. Rarely, it can also put the mum’s health in danger.

The terms mole, hydatidiform mole, and gestational trophoblastic illness are also used to describe molar pregnancies. Even if you have previously experienced a regular pregnancy, this pregnancy problem is still possible. The good news is that, even after a molar pregnancy, you can still have a healthy, fruitful 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

A partial molar pregnancy happens when the mass contains both 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 abnormal growth.

A very small percentage of times, molar cells penetrate the uterus deeper than they should. These cells have the potential to develop into cancer and spread to other bodily regions. This type of mole is invasive. A choriocarcinoma, a type of cancer, can grow from an invasive mole if it is not treated. Fortunately, it is a malignancy with an almost 100% cure rate.

Causes of Molar Pregnancy

You can’t control whether or not you have a molar pregnancy. It’s not caused by anything you did. A molar pregnancy can happen to women of all ethnicities, ages, and backgrounds.

A molar pregnancy is caused by an abnormally fertilised 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 fertilised 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 to 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
  • Pre-eclampsia
  • High blood pressure

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

Sick asian woman vomiting into basin in toilet,Nausea,Indigestible

Image Source: iStock

Implantation Bleeding vs Period

It can be challenging to determine whether light bleeding is an early sign of pregnancy or just regular spotting before your period because implantation bleeding is a symptom that frequently occurs before you test positive on a pregnancy test. Sadly, there is no surefire technique to determine this.

Wait a few more days and use a pregnancy test to determine whether you are or are not pregnant. You might also be able to determine it based on when you last had sex. It’s doubtful that any spotting you’re experiencing is implantation bleeding if it has been more than two weeks.

A third of women who claim they’ve had implantation bleeding often remark it’s different from their typical premenstrual spotting; some say the blood is darker and less red than normal period blood. Some people experience little cramping at the same time as the spotting.

However, the two types of bleeding are very similar for many women. Therefore, if you mistakenly believe that some spotting is implantation bleeding and start your period a few days later or if you mistakenly believe that implantation bleeding is typical spotting and become pregnant, you’re not the only one!

When to call the doctor

Even during times other than implantation, light bleeding during pregnancy is frequently typical. The cervix becoming irritated after a pelvic exam, sex, or a vaginal infection are examples of common causes.

But if you experience bleeding after a positive pregnancy test, you should always call your doctor so you can discuss any additional symptoms. This is because bleeding after a positive pregnancy test can occasionally be an indication of ectopic pregnancy, molar pregnancy, or other early miscarriage.

However, try not to worry too much. There is a strong chance that everything will be alright if the bleeding is minimal and brief.


paid miscarriage leave

The majority of molar pregnancies are discovered after what seems to be a “normal” loss in which the lady has had surgical miscarriage care. This procedure may also be referred to as an ERPC, an “evac,” or a D & C.

In the majority of hospitals, a sample of the excised tissue is submitted to the lab for testing to determine whether it is healthy pregnancy tissue. (This procedure is known as histology, and you could be prompted to give your consent.) Through this examination, molar tissue and a molar pregnancy can be found.

It could take some time before you are informed that you have (or may have) a molar pregnancy after the procedure. You may not hear from us by phone or letter for a few days or even weeks following your miscarriage. Before you can get more information, you could be requested to make another appointment with the doctor.

Who Is at Risk for 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.

  • RhoGAM

RhoGAM is a medication that will be given to you as part of your treatment if you have blood that is Rh-negative. This avoids various issues that can arise when generating antibodies. If your blood type is A, O, B, or AB-, be sure to tell your doctor.

  • 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 the removal of the uterus (hysterectomy). 


Following the removal of your molar pregnancy, you will require additional blood testing and monitoring. It’s crucial to confirm that there was no molar tissue remaining in your womb.

Rarely, the tissue in the mouth can come back and lead to certain malignancies. Up to a year after treatment, your doctor will continue to perform scans and examine your hCG levels.

Later-stage treatment

Yet again, molar pregnancy-related malignancies are uncommon. Most have a survival probability of up to 90% and are also extremely curable. You may need chemotherapy and radiation treatment for some malignancies.

Can the Fetus Survive in a Molar Pregnancy?

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.

sad woman - molar pregnancy article

Image Source: iStock

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.

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.

Updates from Matt Doctor

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