Molar pregnancy: what it is, symptoms, treatment and follow-up

Cancer Research UK explains that a molar pregnancy is a type of gestational trophoblastic disease (GTD), abnormal cells that start in the womb in the cells that would usually develop into the placenta. It is also called a hydatidiform mole. It happens when fertilisation of the egg by the sperm goes wrong, leading to the growth of abnormal cells or clusters of water-filled sacs inside the womb.

It cannot develop into a healthy baby. The NHS says it happens by chance and is rare.

The NHS says a molar pregnancy may not have any symptoms, or you may have some of the usual symptoms of pregnancy. You may find out at your first pregnancy ultrasound scan at around 8 to 14 weeks, or after the pregnancy ends in a miscarriage. Cancer Research UK says many are picked up on routine scans and that the main symptom is vaginal bleeding.

The NHS says to call a midwife or GP if you are pregnant and have any bleeding or a dark discharge, are feeling or being sick often (severe morning sickness), think your bump looks bigger than it should for your stage of pregnancy, or have any other symptoms you are worried about.

If a midwife or doctor thinks you have a molar pregnancy, the NHS says you will need blood tests to check your level of the pregnancy hormone hCG, which is usually higher than normal, an ultrasound scan, and an appointment with a specialist (gynaecologist) or at an early pregnancy assessment unit.

The NHS notes that finding out can be very difficult, and that a doctor or midwife can give advice about available support.

The NHS says a molar pregnancy may end on its own with a miscarriage. If it does not, it is usually treated with a procedure to remove the pregnancy, typically under general anaesthetic so you are asleep. Sometimes medicine can be used instead to end a molar pregnancy. Cancer Research UK says the most common treatment is surgery and that some women have drug treatment.

In a very rare twin pregnancy where one baby develops normally alongside a molar pregnancy, Cancer Research UK says it is sometimes possible for the pregnancy to continue, but with complications it may not be possible, and doctors can refer you to a national molar pregnancy treatment centre for advice.

After treatment the NHS says you will have regular blood and urine tests to check that your hCG level is returning to normal. Cancer Research UK says you are closely monitored.

Very rarely, molar pregnancy cells can remain in the womb and become cancerous. The NHS says this is called an invasive mole or choriocarcinoma, and that it can usually be treated successfully with chemotherapy. Cancer Research UK says that usually any molar cells left after treatment die off by themselves, but if they continue to grow they form a tumour called an invasive mole or persistent trophoblastic disease, which most women need chemotherapy for.

Miscarriage UK says that if hCG levels take longer than eight weeks to return to normal, monitoring continues for six months.

The NHS says you can have sex as soon as you feel ready, but it is important to use contraception while you are having follow-up care, and to talk to a GP about what type is right for you. It says having a molar pregnancy does not affect your chances of getting pregnant again, but you should wait until your doctor tells you it is safe before trying for a baby.

The NHS says a molar pregnancy happens by chance and is not caused by either parent doing something wrong. You may be more likely to have one if you are a young teenager or over 45 when you get pregnant, have had a molar pregnancy before, or have an Asian background. Cancer Research UK likewise lists age and a previous molar pregnancy as factors that might increase the risk.

The NHS says it can take time to recover from a molar pregnancy, both physically and emotionally. The specialists looking after you can advise on support, and the NHS lists organisations including Molar Pregnancy Support & Information, Miscarriage UK and Tommy's. It also names the Charing Cross Hospital Trophoblast Disease Service, one of the national specialist centres.

On the NHS, a molar pregnancy is diagnosed through early pregnancy or maternity services, with follow-up arranged by a specialist trophoblastic disease service. Private early pregnancy scans are available, but follow-up hCG monitoring is generally arranged through the specialist NHS centres.