Molar pregnancy 


Grape-like cysts from a hydatidiform mole 

Emotional effects

While physical recovery is often relatively quick, it can take longer to recover emotionally from a molar pregnancy.

Not only does molar pregnancy involve the loss of a foetus, it also carries the slight risk of a cancerous growth. This can create an enormous emotional strain.

Communicating your feelings with your partner, a doctor, a counsellor, or someone else who has gone through a similar experience can be beneficial.

There are support groups and forums that can help people handle the stress of a molar pregnancy, such as the Molar Pregnancy Support Group and the Hydatidiform Mole UK Information and Support Service.

Read more about dealing with stress, anxiety and depression.

A molar pregnancy is an unsuccessful pregnancy where the placenta and foetus do not form properly and a baby does not develop.

What happens

In a normal pregnancy, the placenta provides nourishment to the developing baby and removes waste products. The placenta is made up of millions of cells known as trophoblastic cells.

In a molar pregnancy, these cells behave abnormally as soon as the egg has been fertilised by the sperm. This results in a mass of abnormal cells that can grow as fluid-filled sacs (cysts) with the appearance of white grapes. These cells grow rapidly within the womb instead of a normally developing baby. The abnormal cells are referred to as a 'mole', which is from the Latin for mass or lump.

Other terms for a molar pregnancy are gestational trophoblastic tumour, trophoblastic disease and hydatidiform mole.

Molar pregnancies are caused by an imbalance in genetic material (chromosomes) in the pregnancy. Most often, this occurs when an egg that contains no genetic information is fertilised by a sperm, or when a normal egg is fertilised by two sperm.

How common is molar pregnancy?

Molar pregnancies are rare, only about one in every 600-800 pregnant women in the UK will develop a molar pregnancy. This amounts to less than 1,500 a year.

Increased risk

Factors that increase the risk of molar pregnancies are thought to include:

  • Age – Molar pregnancies, particularly partial molars (see below), are more common in teenage pregnancies or women over the age of 45.
  • Previous molar pregnancy – If you have had a molar pregnancy before, then the chance of another one is around 10 times higher than if you haven’t.

Types of molar pregnancy

There are two main types of molar pregnancy, depending on the balance of chromosomes in the egg. These are:

  • complete moles, when no normal placental tissue forms and no foetus develops, instead a mass of abnormal cells grow
  • partial moles, when some normal placental tissue forms along with an abnormal foetus, but the foetus does not survive longer than three months

In very rare cases, a twin pregnancy can include a normal foetus and a mole.

Symptoms and diagnosis

In many cases, there are no signs that a pregnancy is a molar pregnancy, although you may get bigger more quickly than usual and suffer with bad morning sickness.

If there are symptoms, the most common is dark-coloured vaginal bleeding. This usually starts to occur about 6-12 weeks after conception.

In most cases, the problem is first spotted during an early ultrasound scan that usually takes place between weeks 10-16 of pregnancy.


Although a mole is classed as a benign growth, which means it is not cancerous, it must be removed surgically. This is done under the care of a gynaecologist.

The operation to remove the mole is called dilatation and curettage (D&C), which involves removing the contents of the womb.

In some cases, molar pregnancy can be treated with the removal of the womb (hysterectomy), but this is usually only if you no longer wish to have children.

Women who have had a molar pregnancy within the UK are registered at the National Trophoblastic Screening Centres. For further information about this, go to the Charing Cross Hospital Trophoblast Disease Service or the The Sheffield Trophoblastic Disease Centre website.

Almost all cases of molar pregnancy are successfully cured.

After treatment

Following the operation to remove the mole, some cells will always be left in the womb. These cells usually die off over time in around 90% of women.

To check this has happened, all women must undergo routine monitoring of the hormone hCG (human chorionic gonadotrophin) via the National Trophoblastic Screening Centre. hCG is the pregnancy test hormone produced by the mole cells. It can be detected in blood and urine tests.

Hormone monitoring will also identify the small number of women who develop a persistent or invasive mole (see below).

It is recommended that you do not get pregnant again until your hormone levels return to normal, which normally happens within two months, but can take up to a year. The risk of reocurrence, while higher than the general population, is still relatively small. The chances of a molar pregnancy happening again is only about 1% and most women go on to have successful pregnancies.


In rare cases, a persistent or invasive mole can develop. There is a 10% chance of this happening, and if it does happen it is classed as malignant (cancerous).

The risk of malignant change of a partial mole pregnancy is 1%. The risk of malignant change of a complete mole is 15%.

Invasive molar pregnancy is usually treated with chemotherapy. There are two treatment centres, one in Sheffield and one in London. For further information, go to the Charing Cross Hospital Trophoblast Disease Service or the Sheffield Trophoblastic Disease Centre website. 

In all cases, malignant moles are successfully treated, usually with only gentle chemotherapy being required.

    For an online patient support group with a chat room visit

    Page last reviewed: 18/09/2012

    Next review due: 18/09/2014


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    The 5 comments posted are personal views. Any information they give has not been checked and may not be accurate.

    Me 2012 said on 15 July 2014

    In 2010 I was pregnant with my first baby, we went for the 12 week scan and my gut feelin was tellin me there was nothing there.

    I went in and they started scanning me and asked how far along I was, I told em I was 12 weeks and that's when she told me my baby had no heart beat and it was only 8 weeks gestation. I had no signs of a miscarriage absoloutly nothing, I was devastated. They gave me a few options as to what I could do and i opted to have a DNC (scraping).

    I'm really glad I did otherwise would not have known about the partial mole I had. However there wasn't enough information and support available to me, there fore I couldn't quite get my head around it. I felt like I didn't get the support I needed and that I was still grieving for my baby and tryin to come to terms with this disease, it was all too much and it lead me to take an overdose. ( very ashamed of myself).

    However after trying again in 2012 I had a healthy boy, it is always in the back of my mind though for future pregnancies.

    Other ladies out there that are or have gone through a similar thing should know they are not on their own and there is more support and info available.

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    Dragonbaz said on 09 November 2013

    In 1979 I had a hydatidiform mole and stillbirth at 31 weeks. The baby's heartbeat only stopped about 20 mins before she was born. She only weighed one and a half pounds with the afterbirth weighing four and a half pounds. Fortunately after sending regular urine specimens to Charing Cross Hospital I was cleared to ' try again '. We subsequently had two beautiful daughters. I'm glad that now with regular scans available this condition is recognised earlier hopefully causing slightly less heartache. It is also good to know there is support now for sufferers of this condition.

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    Chezl85 said on 18 October 2013

    I suffered a molar pregnancy in 2006 and saddened that it happened, but suprised to find out that there is not much awareness of it

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    zz004 said on 28 August 2013

    How disastrous! I didn't even know of such rare occurrence. I only hope that more research is being done on the causes and treatments for molar pregnancy

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    zz004 said on 28 August 2013

    I had no idea there was such a thing as this... Apologies to those who have been in such disastrous cases. If only there were more definitive ways of knowing about this sooner so the problem can be alleviated.

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