Hydatidiform Mole

Registered Charity Number 1076829

A company limited by guarantee, number 3779123

Registered in England and Wales

HM/02/04

You have been diagnosed as having a Hydatidiform Mole, also called a Molar Pregnancy. The loss of your baby is likely to make you feel very sad. In addition this may be the first time you have heard of this condition and so you may also feel shocked, confused and anxious about the future.

The purpose of this leaflet is to explain fully what a hydatidiform mole is, and why it is necessary for women who have had a mole to be followed up by the hydatidiform mole follow-up service. All the information in this leaflet has been carefully checked. It is important that you understand exactly what has happened to you, and why your doctors may recommend a certain course of action. The meaning of the medical or scientific terms we have needed to use is given at the end of the leaflet.

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How a normal pregnancy develops

The sperm meets the egg (or ovum) in the fallopian tube which leads out towards the ovary from where the egg came a few days before. The sperm joins the egg and the fertilised ovum moves on towards the cavity of the womb itself. During fertilisation the genes from the sperm mix with those from the egg to produce the individual features of the baby to be.

Genes, which are found in all of our cells in things called chromosomes, contain a system for passing on genetic information in a series of chains of a chemical called DNA. By the time the fertilised ovum has reached the womb, all the information has been exchanged and it has divided into two main groups of cells.

The trophoblast is that part from which the placenta (afterbirth) and membranes develop. Another name for this tissue is the chorion.

The trophoblast invades the lining of the womb to anchor the pregnancy and allow it to grow. This is called implantation.The placenta forms and so does the embryo. After a few weeks it becomes a recognizable baby (or foetus, as it is called while still in the womb). The baby grows and his or her organs gradually become able to function on their own and, after about 40 weeks since the last period, he or she is born.

Many pregnancies, possibly 50 to 60 percent, are lost before they can implant, or within the first three months. This is called a miscarriage. Rarely, other problems can arise and Hydatidiform Mole is one of these. The rest of this leaflet describes this rare condition.

What is a Hydatidiform Mole?

This peculiar name is an old-fashioned term meaning a liquid-filled mass of cells. It arises when the trophoblast (or chorion) grows in a disorganized way to fill the womb at the expense of the embryo. Since it swells to fill the womb, a hydatidiform mole is one of a group of rare conditions called trophoblastic tumours. The pregnancies are called molar pregnancies. They occur in about 1 in 1200 pregnancies.

There are two types of molar pregnancy: a complete and a partial hydatidiform mole. Occasionally the mole tissue persists and may start to grow and spread; this is an invasive mole. Choriocarcinoma is a very rare complication of hydatidiform mole.

Complete Mole

We have noted that an egg and sperm fuse together and share genetic material (DNA). Sometimes the egg cell does not carry any genetic material so that when the sperm fuses with it, no sharing can take place. Usually the fertilized egg dies at that point but, rarely, it goes on to implant in the womb. When it does, no embryo grows, only the trophoblast, and it grows in a disorganized way. This produces the complete hydatidiform mole.

Partial Mole

In this situation two sperms fertilise the egg (this should be impossible). There is too much genetic material and, as a result, the pregnancy develops abnormally, with the placenta outgrowing the baby. A foetus may or not be present and even if it is present, it does not develop. There have been some

(very few) reports of live babies born after what was thought to be a partial mole, but this may have been the result of an extremely rare condition where a normal baby has a mole for a 'twin'.

Invasive Mole

We have seen that one of the things that trophoblast does normally is to invade into and through the lining of the womb. This is necessary to make the placenta and to hold it in the womb. Sometimes the trophoblast of a complete molar pregnancy invades much more deeply into the womb than it should and, rarely, it can spread. This condition needs to be recognised and treated properly (described below).

Choriocarcinoma

In this very rare tumour the trophoblast cells become totally disorganised

and can invade and spread widely. They have, in fact, become cancerous. Some choriocarcinomas follow a complete molar pregnancy, but extremely rarely it can follow some time after normal pregnancy, miscarriage or termination of pregnancy. It is to be emphasised that this is extremely rare. The small risk of choriocarcinoma is the reason that molar pregnancies are followed up. This is also why the follow-up centres are located in units dealing with cancer (oncology) or trophoblastic tumours. They can detect choriocarcinoma very early and the cure rate is almost 100%.

What do I feel if I am carrying a molar pregnancy? One of the hormones produced by trophoblast normally is called human chorionic gonadotrophin (hCG). One of the functions of hCG is to make the ovary produce its hormones to allow the pregnancy to develop. Most of the symptoms of a molar pregnancy are caused by the massive amount of hCG produced by the overgrown trophoblast. The symptoms will therefore be mainly:

● No periods

● A lot of nausea or vomiting. This can be really troublesome.

● Irregular bleeding from the vagina. The blood may contain little fluid- filled cysts.

● Symptoms like those of a miscarriage between 8 and 16 weeks

The womb is often larger than is expected from your dates and sometimes the hCG causes the ovaries to be enlarged. Rarely, a mole can cause high blood pressure and protein in the urine (pre-eclampsia or ‘toxaemia’), which is a dangerous condition of pregnancy.

How is it diagnosed and treated?

If you go to your doctor and s/he suspects that you have a molar pregnancy, s/he will arrange:

● a very sensitive blood test to measure hCG

● an ultrasound scan

● for you to be seen by the obstetrician/gynaecologist.

If the diagnosis is confirmed, you will be counselled by the gynaecology team. They will advise that you be admitted to hospital and have the mole removed in theatre by a suction instrument passed through the neck of the womb (cervix) while you are asleep under general anaesthetic. This is called surgical evacuation of the mole. You will be observed in hospital for

24 to 48 hours, depending on circumstances. It is important that you understand that this is not a 'termination of pregnancy' or 'abortion'. In most cases there never was an embryo and even in the partial mole it will not develop. You must be reassured so that you do not feel guilty. You may well still feel sad, however, at the loss of your pregnancy.

The tissue will be sent to the laboratory for examination and you will be told the result. (see also 'How can I best help myself?')

A series of tests on your blood and urine for hCG will be carried out over the next few months. If any of the mole has been left behind, the level of hCG may not fall or may even increase. In most women the levels of hCG drop fairly rapidly. If your level of (serum) hCG drops to normal (4 IU/L or less) within 8 weeks, you will be followed up for 6 months from the date of evacuation.

If your hCG level takes longer than 8 weeks to drop to normal, then you will be followed up for a further 6 months after your first normal test. If your hCG values remain the same for three successive samples or they start to rise again, you will be recommended for treatment. These are general rules, and every woman is treated and carefully assessed as an individual.

The results of the follow-up will be sent to your GP and your gynaecologist. If you want to know your own results, you can telephone the follow-up service (allow about three days for them to deal with the sample) and they should tell you the result and how you are doing.

The results from your serum and urine are reported as IU/L (International Units of hCG per Litre). The 'normal' serum level is less than 5 IU/L. Once the follow-up is complete there is no reason why you should not become pregnant.

In future pregnancies, an early ultrasound scan, at approximately 8 weeks, may help to reassure you and your doctor. Antenatal care should be shared between your GP/midwife and the hospital.

Approximately 10% of women require additional treatment using drugs

(chemotherapy). This may involve a stay in hospital during which you will be given a drug or drugs to kill off any remaining molar cells. Treatment is very effective and will not normally affect your ability to have more children.