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Risks and causes

Find out about the causes and risk factors for persistent trophoblastic disease (PTD) and choriocarcinoma.

What persistent trophoblastic disease and choriocarcinoma are

Persistent trophoblastic disease and choriocarcinoma are both rare conditions. They belong to a group of conditions known as gestational trophoblastic disease (GTD for short). 

Persistent trophoblastic disease (PTD)

PTD can occur after treatment to remove a molar pregnancy but some molar tissue is left in the womb and it grows to form a new tumour. In a molar pregnancy the fertilisation of the egg by the sperm goes wrong and creates abnormal cells or clusters of water filled sacs inside the womb.


Choriocarcinomas are extremely rare and develop from cells of the placenta. They happen after 1 in 50,000 pregnancies. There are about 20 cases per year in the UK. They can occur some time after any type of pregnancy (including miscarriages or terminations). Choriocarcinoma is more likely after a molar pregnancy.

What a risk factor is

A risk factor is anything that can increase your chance of developing a particular disease. Each condition has different risk factors.

Remember that having one or more risk factors doesn't mean that you will definitely get GTD. Most people who have one or more of the risk factors never have a GTD, and some people who have none of the risk factors do develop it.

These conditions are very rare and this information is only a guide to what might increase your risk.


Your risk of developing a molar pregnancy and persistent trophoblastic disease changes with age. The risk of developing it is slightly higher in women under the age of 18 and much higher in women over the age of 45.

Ethnic group

Molar pregnancies and persistent trophoblastic disease are slightly more common in women from Asian countries than in women from other ethnic groups. In Asia, and in Asian women living in the UK, there is about 1 molar pregnancy for every 390 babies born, compared to around 1 molar pregnancy for every 590 babies born in the UK.

Previous molar pregnancy

About 10 to 15 out of every 100 women (10 to 15%) who have had a complete molar pregnancy will go on to develop either persistent trophoblastic disease or a choriocarcinoma, and will need treatment with chemotherapy. For women who have had a partial molar pregnancy the risk is only 1 in 100 women (1%).

Information and help

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