The things you need to know!

The information provided on this website is published information provided by Weston Park Hospital, Sheffield and from various other medical websites.

The information you are about to read will refer to the terms ‘molar pregnancy’, ‘hydatidiform mole’ and ‘trophoblastic disease’ which are all essentially the same thing. Please be aware that the information contained herein has been taken from many different websites and that each site may describe a molar pregnancy slightly differently.

Summary Sentence – A Molar Pregnancy is a conception where something goes wrong right at the beginning (misconception).


What is a molar pregnancy?

Trophoblastic disease is an uncommon complication of pregnancy. To understand it we must first look at a normal pregnancy. This consists of two 'parts' developing in the womb.

The foetus or developing baby, the placenta (or after-birth), which has many functions including the feeding of the baby and the removal of its waste products. The placenta is made of millions of cells called trophoblasts.

These two parts normally develop together, in parallel, the end result being a healthy baby and a placenta which is no longer needed, so the latter is expelled just after the baby is born (afterbirth).

In trophoblastic disease there is an abnormal overgrowth of all or part of the placenta, causing what is called a molar pregnancy or hydatidiform mole. The term seems strange but is similar to that used for a harmless growth on the skin, which is also called a mole.

As with skin moles, a hydatidiform mole is often harmless. However, it can keep growing and, if left untreated, can bury itself into the organs around it, including the uterus (womb) and even spread via the blood to other distant organs including the lungs, liver or brain. It is once it has reached this stage that it can have serious effects.

Although a hydatidiform mole is not cancer and rarely even becomes cancerous, it can behave in similar ways. Most of the treatment is aimed at stopping the disease process long before any of these things happen.

Different types/stages of moles:

  • Hydatidiform mole
  • Partial Mole
  • Complete Mole
  • Persistent Gestational Trophoblastic Disease
  • Choriocarcinoma

The commonest kind of trophoblastic disease, where the overgrowth is benign but may spread to other parts of the body if not treated. This is further subdivided into:


Where part of an apparently normal placenta overgrows (proliferates) and part develops normally. There may be a developing foetus present, but this is genetically abnormal and cannot survive outside the womb. This is where two sperm enter the egg and instead of forming twins forms an abnormal foetus.


Where the whole placenta is abnormal and usually grows very rapidly. There is no developing foetus in these pregnancies. This is where one sperm enters the egg but only half of one set of chromosomes are present and do not develop into a foetus.


Where part of the mole remains in any part of the body despite initial treatment by the gynaecologist. Even a tiny amount of mole anywhere in the body can grow quickly and cause problems, so active treatment of this condition is very important.


A very rare but curable form of cancer where the placenta becomes malignant. This can arise from a molar pregnancy or an otherwise normal pregnancy or miscarriage. Choriocarcinoma can also spread throughout the body, usually to organs like the lungs, liver and brain.


What causes it?

Molar pregnancy is thought to be caused by a problem with the genetic information of an egg or sperm. Factors that may increase your risk of having a molar pregnancy include:

  • Age. Risk for complete molar pregnancy steadily increases after the age of 35
  • History of molar pregnancy, particularly if you've had two or more
  • Possible ovulatory disorders
  • History of miscarriage
  • A diet low in carotene (a form of vitamin A). Women with low carotene or vitamin A intake have a higher rate of complete molar pregnancy
  • Living in certain geographic locales (especially Southeast Asia and Mexico)

It is however, worthwhile noting, that the number of times a women has been pregnant doesn't influence her risk.



As so little is understood about how and why hydatidiform moles occur, they're difficult to prevent. However, good healthy nutrition may decrease the risk of one developing and any other common pregnancy complications.



The diagnosis of a molar pregnancy is usually established by the pathologist when he/she looks at the placenta under a microscope. This may be done after a miscarriage, termination of pregnancy or ectopic pregnancy. A mole may be suspected for several reasons in an ongoing pregnancy, for example if the womb is larger or smaller than it should be for the stage of the pregnancy, or if you are being sick more than in a normal pregnancy.

Complete hydatidiform moles also have a characteristic appearance on an ultrasound scan so this, and the fact that no developing foetus is seen when you have a scan at the ante-natal clinic, can allow the diagnosis to be suspected.

Treatment may be a medical evacuation (tablets are inserted into the vagina and taken orally) or a dilatation and curettage (D & C, or "scrape") to remove as much of the molar tissue from the womb as possible. This is a minor operation which is carried out after most miscarriages under a general anaesthetic. In most cases, one or two of these minor operations will be enough to remove the mole permanently.

In a normal pregnancy the placenta makes many hormones to support itself, the baby and the mother. One of these hormones is called human chorionic gonadotrophin (hCG), and in a molar pregnancy, where there is overgrowth of the placenta, there is a large amount of this hormone produced.

BhCG circulates in the mother's blood and hCG is excreted in her urine. These can be readily measured in the laboratory from blood or urine samples. This is useful in helping with the diagnosis of the condition, but even more useful in helping decide when a patient is cured. When there is no disease in the body, the level of BhCG in the blood and hCG in the urine is low. When there is a lot of disease the level is high. As the disease resolves the levels fall gradually. These tests are important because it is possible to monitor how your disease is progressing.

Once the diagnosis of trophoblastic disease is made, you will be registered with the regional centre which specialises in the monitoring of the disease. For those living in the upper half of Northern England and Northern Wales you will be referred to Sheffield – South Yorkshire all other referrals including Ireland are referred to London. There is also a screening/follow up centre based in Dundee that provides follow ups, but no treatment. You will be posted urine sample bottles, and a box in which to post them back. In a laboratory at the regional centre, the level of hCG will be measured and compared with previous levels. All being well, your hCG level will quickly become low and remain so.

Please refer to your regional centre for specifics as follow up procedures between centers may differ slightly.

However, as mentioned earlier, even a tiny amount of mole tissue left in the body can grow and spread via your blood stream and this can happen up to many months after apparent cure. Thus your disease will probably be monitored by urine samples for a period of around six months. The intervals between samples become longer if the hCG levels remain low.

However, if the level stays high or starts to rise, this will be detected at the special regional centre. The centre will notify your gynaecologist, who will then contact you. In some cases drug treatment in the form of chemotherapy is required to eliminate any remaining disease. You are more than welcome to call the centre for your urine results. Up to 10% of women require further treatment in the form of chemotherapy if their hCG hormone levels do not reduce on their own or remain the same.

All this is relatively straightforward. However, because we assess your disease by measuring a hormone normally only seen in pregnancy, if you become pregnant during the course of your follow-up with urine samples, the healthy pregnancy will result in the rapid rise of hCG levels in your urine, which might lead to unnecessary worry and confusion.


Placental site trophoblastic tumour

More information can be found on the CancerHelp website.


Genetic origin of a Hydatidiform Mole

This section is to help you understand more what actually happens at fertilisation when a hydatidiform mole occurs.

Terms used –


Involving or resulting from a single sperm cell


The entrance of two spermatozoa into one egg

Normal Conception
diagram of normal conception
Partial Mole
diagram of partial mole
Monospermic Complete Mole
diagram of complete mole
Dispermic Complete Mole
diagram of dispermic complete mole



Pregnancy following too soon after trophoblastic disease may also increase the risk of recurrence or re-activation of the mole. You are advised to avoid pregnancy for around six months with normal urine hCG levels or until your consultant gives you the go ahead.

For similar hormonal reasons, use of the oral contraceptive pill is not recommended until the hCG levels are normal. We also advise avoiding 'coil' contraception until normal menstrual cycle is re-established. To be safe, alternative methods of contraception should be used for this time for instance condoms or the cap with spermicidal foam.


Treatment Regimens

Up to 10% of diagnoses require additional treatment other than the D and C and urine testing follow up. This is in the form of chemotherapy.

Each individual’s case is different but the vast majority of patients begin on Methotrexate. This is also used for arthritis and skin conditions. It is administered by intra-muscular injections (buttock) followed by a Folinic Acid (NOT folic acid) tablet exactly 24 hours later. The usual regimen is to have four injections on alternate days with Folinic Acid in between but regimens differ at different treatment centres. You will stay as an in-patient for the first part of the course of treatment as the chemotherapy could cause heavy bleeding and other side effects. You will then continue as an outpatient either at your treatment centre or it may be possible to arrange it at your local hospital to avoid commuting long distances.

As mentioned previously measurements of BhCG are used to monitor treatment response. It is essential with all chemotherapy regimens that BhCG is measured regularly. In general an adequate treatment response is defined by a 50% reduction after each course of chemotherapy.

The level of BhCG may reach normal (different regions aim for different levels between 2-5) or become undetectable when there is still a residual tumour burden of cells. Therefore with all regimens, treatment is continued for at least six weeks.


Methotrexate Regimen

Intramuscular injection (buttock), alternate days x 4 doses per cycle.  Folinic Acid, orally, 24 hours after each injection. – to protect internal organs from damage from the Methotrexate. Seven day rest between treatment cycles.

When returning to your treatment centre on the 1st day of each new course of chemotherapy, you will have several blood tests to measure your blood count, blood platelets, Haemoglobin, liver function test and BhCG hormones. Depending on your test results and your hormone levels you will be able to continue the Methotrexate programme for another cycle.

This regimen applies only to Sheffield Treatment Centre. For further information on how London Treatment Centre works please contact them directly.

Common known side effects of Methotrexate

It is very important to drink 2 to 3 litres of water every day to flush the toxins from your body from the treatment (this can also come from juice, tea etc).

  • Oral mucositis (sore gums and mouth) – Treated with analgesic mouthwash and low dose corticosteroid lozenges.
  • Gritty or runny eyes – Treated with eye drops.
  • Cold like symptoms - Treated with simple analgesia or even anti-histimines have been known to work well.
  • (Serious) Pleurisy – Treated with simple analgesia. (On rare occasions this problem can be very severe and may need an alteration in therapy despite adequate tumour response).

Further treatment

Approximately 20% of all low risk patients will require alternative treatment because of the development of Methotrexate resistance (BhCG levels fail to drop or even increase). Such patients can be treated with the combination of Dactinomycin (Actinomycin D) and Etoposide or single agent Dactinomycin.

Dactinomycin (Actinomycin D/Act-D) and Etoposide Regimen

Such patients have been successfully treated with the combination of Dactinomycin (Actinomycin D) and Etoposide. These drugs are given for three hours at a time intravenously for three days each cycle with a fourteen day rest between cycles.

This regime applies only to Sheffield Treatment Centre. For further information on how London Treatment Centre works please contact them directly.

Common side effects of Dactinomycin (Actinomycin D/Act-D) and Etoposide
  • Vomiting - Treated with simple anti-sickness drugs
  • Alopecia (hair loss) - Total alopecia is usual but hair will fully return once treatment finishes.
  • Bone Marrow Toxicity - Treatment - G-CSF may be prescribed should this problem lead to delays in drug administration. This is an injection which stimulates your body to produce white cells that can fight infection.

Duration of follow-up procedures

For those who do not require chemotherapy they will require 6 months of urine testing. You should be able to conceive again six months from the moment your levels hit normal.

For those who do require chemotherapy they will require BhCG analysis weekly for the first 6 weeks and then monthly for the subsequent 6 months. This then moves on to quarterly bloods and urine tests then every 6 months for life. If levels remain satisfactory you should be able to conceive again 12 months from the moment you stop chemotherapy.

This regime applies only to Sheffield Treatment Centre. For further information on how London Treatment Centre works please contact them directly.


Cure rate of Molar Pregnancies

The prognosis depends on the extent of disease and the aggressiveness of treatment. The cure rate is very good.

If metastatic (disease in other parts of the body) trophoblastic disease is vigorously treated, the cure rate is also 100%.

Widely metastatic disease if recognised promptly and treated aggressively with multi-agent chemotherapy (cocktail) and surgery, the cure rate is about 80%.


Further pregnancies

If a woman has a molar pregnancy, her outlook for a future pregnancy is good. The risk that a mole will develop in a future pregnancy is only one to two percent. The vast majority of couples go on to have healthy babies.

You may be especially concerned about becoming pregnant again in the future. However, it is highly unlikely that you will suffer another molar pregnancy. In fact, the chance of experiencing a second molar pregnancy is only about 1 in 100. The vast majority of couples go on to have healthy babies.

As mentioned in the follow up section it is usually recommended that those who have had treatment wait at least one year from the point of treatment finishing before becoming pregnant again. This is because your BhCG levels need to be continuously monitored at regular intervals for signs of the mole returning and also to allow the chemotherapy to leave your body – chemotherapy can cause devastating results in pregnancies. After the mandatory one-year wait, you should receive the all clear from your treatment centre/consultant and can start trying again.

This is the standard remission time but each individual is different.


Emotions and molar pregnancies

Having a molar pregnancy can challenge your emotional and physical well-being. Grief about losing a pregnancy, combined with fear of cancer, may feel like more than you can handle.

For most women the emotional healing takes much longer than the physical healing from surgery. Even if the pregnancy ended very early, the sense of bonding between a mother and her foetus is often very strong. The feelings of loss can be extremely intense for some couples.

Grief can involve many feelings. One may find oneself looking for reasons why the pregnancy ended. You or your partner may wrongly blame yourselves (or secretly each other). Sickness can manifest itself in the form of headaches, loss of appetite or tiredness.  There may be problems with concentrating or sleeping.

Never underestimate unexplained miscarriages, and having to cope with a Molar Pregnancy on top of this is shattering. For those diagnosed with a complete molar they have to come to terms that there was never an embryo or baby. This can be quite destroying especially when the body produces all the normal signs of being pregnant. Although painful, still acknowledge that you conceived and that you and your partner still created something. And if it helps hold a ceremony/memorial for your lost one (no matter how early or late into pregnancy you were) for closure. It will be hard if you are receiving treatment months down the line. Maybe consider it once your treatment has finished then you don’t have that constant reminder of what has happened.

The feelings of grief are usually different between the man and woman; after all, it is the woman that has felt the physical changes of pregnancy.

Many men believe that they must be “strong” under these circumstances and so choose not to express their feelings to their partners in an attempt to avoid burdening her with the feelings of hurt and disappointment that he has. This may cause unnecessary tensions between the two of you.

Talking to each other in a very honest manner is the best way for a man to assist both his partner and himself in the recovery process.  Letting her know that she is not alone in her grief can be a true comfort for her. Crying together, explaining yourself and listening to your partner may help on the road to recovery for the both of you.

If either of you are having trouble handling your feelings, try talking to your doctor or close friends or family or even a qualified counsellor. They may not understand your condition but sometimes it helps to talk to someone neutral who can have an objective view on your situation.

Most importantly of all, don't blame yourselves for the pregnancy loss.

An early pregnancy loss does not mean that you cannot have any more children.  The vast majority of women that suffer an early pregnancy loss have a healthy pregnancy later, but do not rush to your decisions too quickly, be sure that both of you are emotionally healed and strong enough to make another attempt.


Adjusting to a loss

It can take 2 or more years to go through a grieving process. The length of time spent grieving depends on your relationship with the lost person, object, or way of life. Even after 2 years, you may re-experience feelings of grief, especially over the loss. Be prepared for this to happen when coming into contact with other pregnant women, newborns, children and most importantly on the anniversary of your due date as these typically revive feelings of grief.

Some grief experts consider grieving to be the slow recovery from a crisis of attachment: After losing something or someone to whom you are deeply attached, your sense of self and security is disrupted. As you adjust to a major loss, your goal is therefore to develop or strengthen connections with other people, places, or activities. These new parts of your life are not meant to replace what you have lost. Instead, they serve to support you as you begin to start a new phase of your life.

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