Molar pregnancy

What is a molar pregnancy?

Molar pregnancy is one of a number of rare conditions that are called gestational trophoblastic disease (GTD). A molar pregnancy happens when there is a problem with the joining of the egg and sperm at the time of conception. The fertilised egg either never develops into an embryo (this is called a complete mole) or it develops abnormally and cannot survive (this is a partial mole).

In normal pregnancies, the fertilised egg contains 23 chromosomes from the father and 23 from the mother. In complete molar pregnancies, the fertilised egg contains no chromosomes from the mother and the chromosomes from the father’s sperm are duplicated. This means that there are 2 copies of chromosomes from the father and none from the mother. In this case, there is no fetus (baby), amniotic sac or any normal placental tissue, instead, the placenta forms a mass of cysts.

In partial molar pregnancies, the fertilised egg contains the normal 23 chromosomes from the mother, but double the chromosomes from the father, resulting in 69 chromosomes instead of the normal 46. This happens when chromosomes from the sperm are duplicated or when 2 sperm fertilise the same egg. In this case, there is some normal placental tissue among the cluster-like mass of abnormal tissue.

The fetus may begin to develop, or just some fetal tissue or an amniotic sac. Unfortunately, even if a fetus is present, in almost all cases it is so abnormal that it cannot survive.

It can be scary and upsetting to lose a pregnancy in this way, but with correct treatment, you are unlikely to experience any long-term physical problems.

How common are molar pregnancies?

About 1 in every 600 pregnancies are a molar pregnancy in the United Kingdom. Your chances of having a molar pregnancy are higher if you:

• are under the age of 20 or over the age of 40.
• have had a previous molar pregnancy (1 in 100 chance).
• are Asian – Asian women are twice as likely to have a molar pregnancy.

How would I know if I had a molar pregnancy?

Almost all women with a complete molar pregnancy have vaginal bleeding in the first 3 months of pregnancy. The symptoms usually mimic those of a miscarriage. Bleeding can start as early as 6 weeks into your pregnancy or as late as

12 weeks. You might also have severe nausea and vomiting, abdominal cramping and abdominal swelling (your womb may grow more rapidly than usual). Women with a complete mole may have an unusually enlarged womb for the stage of the pregnancy.

If you do have a molar pregnancy, an ultrasound will show cysts that look like a cluster of grapes in your womb, and your levels of the pregnancy hormone human Chorionic Gonadotrophin (hCG) will be higher than normal.

What is the treatment for a molar pregnancy?

If you are diagnosed with a molar pregnancy, you will need a small procedure to remove the abnormal tissue. This procedure is done under general anaesthetic (while you are asleep). Your nurse or doctor will talk to you about this in more detail.

All tissue taken during this operation will be examined in the hospital laboratory to confirm the diagnosis. Once we have received the results we will contact you, this can take up to 4 weeks. While we are waiting for the results you may be asked to return to the hospital for a blood test to make sure that your pregnancy hormone (hCG) levels are falling.

Registration of women with molar pregnancy

If the diagnosis of a molar pregnancy is confirmed, you will be registered with the Medical Oncology department of Charing Cross Hospital in London. Charing Cross have an information leaflet available on their website, the web address is at the end of this page.

This registration is essential to monitor your pregnancy hormone (hCG) levels until they go back to normal and to advise you about future pregnancies.

Follow up of women with molar pregnancy

Specialists at Charing Cross Hospital will want to monitor your levels of the pregnancy hormone (hCG) over a period of weeks to make sure they are declining and there is no molar pregnancy tissue left. Follow ups can continue for up to 1 year and usually consists of sending blood and urine tests to Charing Cross Hospital in special kits that will be provided. It is usually not necessary to attend the hospital for this as the blood test can be done at your GP’s surgery.

If you are diagnosed with Gestational Trophoblastic Disease (GTD) by the team at Charing Cross, treatment with chemotherapy will be advised. Your doctor or nurse will discuss this with you.

When can I try to get pregnant again?

You will need to avoid a further pregnancy until your follow-up care is complete and your pregnancy hormone levels have returned to normal. The team at Charing Cross will be able to advise you about when is safe to try for pregnancy.

If you become pregnant before your pregnancy hormone levels have returned to normal, they would rise and it would be difficult for your nurse/doctor to know whether abnormal tissue was growing back. Therefore, we would advise you to use condoms (or other forms of contraction) until your test results are back to normal.

The team at Charing Cross Hospital will advise you not to use hormonal contraception until your pregnancy hormone levels are back to normal.

A molar pregnancy does not affect your fertility or your ability to have a normal pregnancy, even if you have had chemotherapy. You are not at any increased risk for stillbirth, birth defects, premature delivery or other complications and the likelihood of having another molar pregnancy is only 1 to 2 in 100 cases.

In any pregnancy following a molar pregnancy, we will offer you an ultrasound examination at around 8 weeks to make sure all is well. You can contact the Early Pregnancy Clinic directly to arrange this (the contact details are at the end of this page).

How can I cope with my sense of fear and loss?

Having a molar pregnancy can be frightening and upsetting for both you and your partner. If you would like to discuss this, please contact your GP.

Contact information

If you have any questions or concerns, please contact your GP or:

Early Pregnancy Clinic

Gloucestershire Royal Hospital

Tel: 0300 422 5549

This line is open from 8:00am to 4:00pm, 7 days a week.

Further information

If you would like any further information or would like to talk to someone, please contact:

The Miscarriage Association c/o

17 Wentworth Terrace, Wakefield, Yorkshire WF1 3QW

Tel: 01924 200 799

Website: www.miscarriageassociation.org.uk

Charing Cross Hospital

Website: www.hmole-chorio.org.uk