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Molar pregnancy – hydatidiform mole

What is a molar pregnancy?

A molar pregnancy, or hydatidiform mole, is a pregnancy in which the placenta develops abnormally following the fertilsation of the egg by the sperm. This results in uncontrolled growth of the placenta which fills the uterus (womb). For every 1000 live births only 1-2 molar pregnancies are diagnosed.

Sadly, a molar pregnancy is a form of early pregnancy loss. This pregnancy, therefore, will not continue and result in a baby. However, there is a good chance that your next pregnancy will be normal.

There are two types of molar pregnancy: a complete and a partial hydatidiform mole.

  • Complete mole
    Complete mole is when a sperm fertilises with an empty egg. In this case the cells are entirely of paternal origin (from the father). When this fertilised egg grows, there is no embryo (baby) in the pregnancy sac, and only the placenta continues to develop in an abnormal fashion.
  • Partial mole
    These are much more common. In this type of molar pregnancy, the egg is fertilised by two sperm. The resulting embryo has three sets of chromosomes rather than the usual two, so the fetus cannot survive and develop into a baby.

Will you have any symptoms?

There are often no signs that a pregnancy is a molar pregnancy. It may only be spotted during a routine ultrasound scan. Some women can have vaginal bleeding or dark discharge, morning sickness or an unusually swollen tummy.

How is a molar pregnancy diagnosed?

An ultrasound scan and an elevated pregnancy hormone (Human Chorionic Gonadotrophin- hCG) blood test may result in suspicion of a molar pregnancy. The final diagnosis, however, is made by a pathologist after a sample from the pregnancy tissue in the womb is sent to the laboratory for analysis.

How is a molar pregnancy treated?

We would strongly advise admission to hospital to have a surgical management of miscarriage (SMM) performed under general anaesthetic.

Will you need any further follow up?

Yes, once the molar pregnancy has been confirmed by the pathologist after you have had your surgical procedure (SMM). You will be registered with the Gestational Trophoblastic Disease Centre based at Charing Cross Hospital in London. You will then be followed up until your pregnancy hormone (hCG) levels have returned to normal. If a complete molar pregnancy has been diagnosed, follow up will be for 6 months. For a partial molar pregnancy this will be until the hCG levels return to normal (usually 2-3 months)

You will be registered at Charing Cross Hospital and will receive a letter from the follow-up centre confirming your registration for follow-up care. The hospital will organise all your blood and urine tests from London. You do not have to travel to London for the tests as these can be sorted locally and sent to Charing Cross Hospital. Testing is usually every two weeks.

It is important to be followed up properly as occasionally the molar tissue may remain and grow deeper into the wall of the uterus (womb) causing Persistent Trophoblastic Disease for which further treatment is required.

Very rarely a hydatidiform mole can develop into a choriocarcinoma which is a form of cancer and whilst the cure rate is almost 100%, it is important that you attend any follow up appointments arranged.

When can you get pregnant again?

Further attempts at trying to conceive a pregnancy should be delayed until the end of the follow up period.

What contraception can you use?

All contraceptives are safe to use straight after surgical treatment has been performed apart from the IUCD (Coil). This includes hormonal contraception which can be started immediately after uterine evacuation. An IUCD can be inserted once the pregnancy hormone (hCG) levels have returned to normal.

What are your chances of another molar pregnancy?

The chances of having a perfectly normal pregnancy are very good. The risk of a further molar pregnancy is 1% (1 in 100) of women who have been registered at Charing Cross Hospital.

Useful contact numbers

Stoke Mandeville Hospital
Early Pregnancy Unit (EPU) Clinic 8.00am—5.00pm Monday—Friday
EPU Nurse/EPU Bookings 01296 316469
Reception 01296 316264
Ward 16B 01296 418111/8110
Surgical Assessment Unit (SAU) 01296 316500

Further help and advice: The Miscarriage Association c/o Clayton Hospital Northgate, Wakefield, West Yorkshire WF1 3JS Tel (Helpline): 01924 200799

The Gestational Trophoblastic Tumour Screening Unit Department of Medical Oncology, Charing Cross Hospital Fulham Palace Road London W6 8RF
Tel: 020 8846 1409