Molar pregnancy

A molar pregnancy (sometimes called a hydatidiform mole) happens when there is too much or too little genetic material in a fertilised egg and a baby can’t develop. Clusters of abnormal cells or water filled sacs may develop in the womb instead.  

If you are going through molar pregnancy at the moment, we’re really sorry. We know it has the same impact as any other type of baby loss. Most people don’t know what a molar pregnancy is and how it might affect you physically and emotionally. This can make dealing with your loss and the follow up treatment even harder to cope with. There are charities and organisations who can support you – we’ve shared them lower down this page

On this page

What is a molar pregnancy

Types of molar pregnancy

Symptoms of molar pregnancy

When should I get help

Causes of molar pregnancy

Treatment and follow up for molar pregnancy

Gestational trophoblastic neoplasia

Getting pregnant after molar pregnancy

Getting support with molar pregnancy

What is a molar pregnancy?

A molar pregnancy (sometimes called a hydatidiform mole) is one of a group of conditions known as gestational trophoblastic disease (GTD). Molar pregnancies are rare (about 1 in 600 pregnancies). 

Types of molar pregnancy

There are 2 main types of molar pregnancy. Sadly, neither can develop into a baby.

Complete mole

Complete moles usually happen when a single sperm fertilises an ‘empty’ egg which has no genetic material inside. Because of this, a baby does not develop. There will only be molar tissue (other cells) in the womb. Even so, you will get a positive pregnancy test and may feel pregnant. Finding out that there is not a baby there can feel like a real loss, like other types of miscarriage.

Partial mole

Partial moles happen when 2 sperm fertilise a normal egg or 1 sperm fertilises an egg with double the amount of genetic material inside. In a partial mole, there are usually some early signs of a baby among the molar tissue, but this can’t develop into a baby. Again, you will get a positive pregnancy test and may feel pregnant.  

What are the symptoms of a molar pregnancy?

There are often no specific symptoms of a molar pregnancy. 

You may only find out during a routine ultrasound scan at 8-14 weeks or during tests that are done after a miscarriage.

Some women or birthing people with a molar pregnancy have:

• vaginal bleeding or a dark discharge from the vagina in early pregnancy (usually in the first trimester) – this may contain small, grape-like lumps
• severe morning sickness 
• signs of infection including a high temperature (if the molar pregnancy causes an infection in your womb)
• an unusually swollen tummy. 

Some of these symptoms are quite common in pregnancy and aren't necessarily a sign that anything is wrong with your baby. It’s worth getting checked out just in case.  

Most molar pregnancies are diagnosed before 14-16 weeks of pregnancy. If you are over 14-16 weeks pregnant and have a molar pregnancy you may have these symptoms:

• high blood pressure
• protein in your wee (proteinuria)
• symptoms of an overactive thyroid gland (such as tiredness, weakness, twitching or trembling)
• stomach pain (because of large ovarian cysts).

When should I get help?

Contact your midwife or GP if you think you have any of these symptoms.  

You will be referred to an early pregnancy assessment unit (EPAU) for an ultrasound scan. If you’ve had a molar pregnancy before and you think you have another, you can contact the EPAU yourself without contacting your midwife first.

As well as a scan, you will also have a blood test, which measures the amount of a pregnancy hormone called human chorionic gonadotrophin (hCG). This is usually much higher in molar pregnancies than in other pregnancies.  

Doctors may also discover a molar pregnancy after a woman has a miscarriage if the tissues are looked at under a microscope.

What causes a molar pregnancy?

Molar pregnancies are caused by problems with the genetic information in an egg or sperm. We don’t know exactly what causes the problem to happen. We do know that there are some things that can increase your risk.

Risk factors are not the same as causes. Lots of people who have all the risk factors will not develop a molar pregnancy and some people who have none of them will still have one.

Your age. Molar pregnancies are more common in teenage women and birthing people and those over.

Your ethnicity. Molar pregnancies are about twice as common in women and birthing people of Asian origin. Sadly, we don’t know why. More research is needed.

Your pregnancy history. 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 2 or more molar pregnancies, your risk of having another is between 1 in 5 and 1 in 6.

Your diet. Women and birthing people who have a diet that is low in carotene (vitamin A) have a higher risk of molar pregnancy. 

Treatment and follow up for a molar pregnancy

Unfortunately, a molar pregnancy cannot develop into a baby and will need to be taken out of your womb. You will probably need surgery to remove the molar tissue. This will usually take place at the hospital where you have been treated already.

In the UK, you will be registered with a specialist centre for follow-up. This is so your treatment is provided by doctors who are experts in this field. These centres are in hospitals in  London, Sheffield and Dundee. The centres also offer support and counselling if you need it.

After registering with a specialist centre, you will have follow-up appointments. Your specialist centre will ask you to have regular blood or urine tests done at your local GP surgery. These are done to check if your hCG levels are going back to normal.

The length of follow up treatment will depend on your situation and whether you had a partial or complete molar pregnancy.

It’s important to complete these follow ups to ensure that any further complications are found and treated quickly.

“The specialist centres have support groups, information sessions, counselling etc and provide really good specialist support, which helps make navigating a molar pregnancy and the next steps easier. Our experience with Charing Cross was excellent.”

Robyn

Gestational trophoblastic neoplasia (GTN)

Very rarely, a molar pregnancy can lead to gestational trophoblastic neoplasia (GTN). GTN is a rare form of cancer. This sounds frightening, but it has a cure rate of over 99%.

GTN happens when some of the molar pregnancy tissue is still in the uterus. It is usually diagnosed if your hCG levels do not return to normal or if you have persistent or irregular bleeding after a molar pregnancy.

What happens if I have GTN?

You will usually need to have further treatment from the specialist centre you are registered with. This may involve a second operation to remove any tissue from your womb or chemotherapy.  

Treatment is continued until 6 weeks after your hCG level has returned to normal. In very rare cases, some women may need to have a hysterectomy (removal of the womb).

If you have chemotherapy for GTN, your periods will usually restart 2 to 6 months after the end of chemotherapy. Your fertility (ability to get pregnant) is usually not affected.  

Your specialist centre will talk to you about the treatment you need and any side effects.  

Getting pregnant after molar pregnancy

The risk of having another molar pregnancy is small (about 1 in 80).

It’s best not to try getting pregnant again until all your follow-up treatment has finished. For most women and birthing people, this will take about 6 months, although for some it may be earlier or later. A new pregnancy will cause your hCG levels to rise again and this could prevent doctors from identifying if you have developed GTN from your molar pregnancy.

Let your doctor know straight away if you do get pregnant while you are still being treated. They will need to continue follow-up treatment after this pregnancy.

If you have GTN, you will need to wait for 12 months after you have finished chemotherapy treatment. This is because GTN can sometimes come back. This is rare and happens to around 3 in 100 women.

Contraception

You should use barrier methods of contraception such as condoms or a diaphragm until your hCG levels are normal.  

You should not have an intrauterine contraceptive device fitted until your hCG levels have returned to normal. This is because it can cause a puncture in the uterus after a molar pregnancy.

Once your hCG levels are normal, you may use all types of hormonal contraception including the combined contraceptive pill, progestogen only pill, progestogen injection and progestogen implant.  

Talk to your healthcare team about what contraception will be best for you.

Getting support for molar pregnancy

Many people find it hard to move forwards after a molar pregnancy. You may feel grief, sadness and confusion as with any other type of loss. On top of this you may be feeling ‘in limbo’ as you wait for the follow up treatment to finish – and worried about possible complications.  

You may find it helpful to:

• talk to your partner, family or friends about how you feel
• ask your care team what support is available – they may refer you to a counsellor who specialises in support for people affected by molar pregnancy  
• talk to a Tommy’s midwife free of charge from 9-5 Monday to Friday on our helpline: 0800 0147 800 or email [email protected]  
• visit Molar pregnancy Support and Information, MyMolarPregnancy.com or The Miscarriage Association’s support for molar pregnancy, including a Zoom support group
• Read women's stories about their molar pregnancies.

Two of the most important things are to not blame yourselves and not to give up hope. Talk about your feelings and emotions with your partner and try to contact others in your local area who have experienced what you are going through. You are never alone.”

Sue