Molar pregnancy is one of a group of uncommonly occurring conditions called gestational trophoblastic disease (GTD) that occurs when a pregnancy does not develop properly. There are two types of gestational trophoblastic disease:
- Molar pregnancy.
- Gestational trophoblastic neoplasia- this condition will not be covered in great detail on this page.
What happens in the development of a normal pregnancy?
In a normal pregnancy an embryo (baby) develops when a sperm (from the father) fertilises an egg (from the mother). The genetic material from each combines to produce a baby which has half its chromosomes (genetic material) from each parent.
What is a molar pregnancy?
A molar pregnancy is sometimes also known as a hydatidiform mole. It occurs in less than 1 in 700 pregnancies. It is the result of an imbalance in the number of chromosomes supplied from the mother and the father and cannot develop into a normal baby. There are two types of molar pregnancy:
- Complete molar pregnancy: In this type of pregnancy all the genetic material is from the father and therefore there is no development of the fetus (baby) and only the placental tissue (afterbirth) grows. It is the more serious of the two types and is more likely to need additional treatment.
- Partial molar pregnancy: In this type of pregnancy, there is some early development of the fetus but the baby has three sets of chromosomes (two sets of chromosomes are normal) and the pregnancy always fails. The placenta grows abnormally.
The only way to definitely diagnose a molar pregnancy is to send the pregnancy tissue to the pathology lab and test it.
What are the symptoms?
Some women with molar pregnancy do not get any symptoms at all and are diagnosed when they have an ultrasound scan during pregnancy. Some women can get symptoms that include:
• Missed period and a strong positive pregnancy test.
• A lot of nausea (feeling sick) or vomiting.
• Irregular bleeding from the vagina.
• Symptoms similar to those experienced in a miscarriage.
How is a molar pregnancy diagnosed and treated?
- Pelvic Ultrasound Scan: Complete molar pregnancies can be strongly suspected on an ultrasound scan because they have a particular appearance on scan. Partial molar pregnancies are harder to diagnose by ultrasound scan.
- Test of pregnancy tissue (Histology): The only definite way to diagnose a molar pregnancy isto examine the pregnancy tissue in a laboratory. Most molar pregnancies are diagnosed in this way after you have had surgical treatment for miscarriage. At the end of the procedure the pregnancy tissue that has been removed is sent to be examined with your permission.
It may take several weeks for these results to be processed. If molar pregnancy is diagnosed you will be informed.
How is a Molar pregnancy treated?
There are two ways to treat a molar pregnancy. Your doctor will discuss them with you and may recommend one over the other. These options include:
- Surgery – This is the preferred choice of treatment in most molar pregnancies. If your doctor suspects that you have a complete molar pregnancy you will be offered surgery. This is usually done under general anaesthetic. The pregnancy tissue is removed from your uterus and sent to the pathology laboratory to check the diagnosis. You are normally able to go home the same day but may need to stay overnight.
- Medicine – This is an alternative option if a complete molar pregnancy is not suspected however it can be more difficult to obtain sufficient tissue for the laboratory to make a definite diagnosis. Medication is given to cause the molar pregnancy to miscarry. You may need to stay in hospital until you have passed the pregnancy tissue. The pregnancy tissue is then collected and sent to the pathology laboratory to check the diagnosis.
- Expectant management (wait and see) – This option is not recommended when a molar pregnancy is suspected.
Follow up at a specialist centre
If you are confirmed to have a molar pregnancy we recommend that you are entered into a specialist follow up programme. The doctor will ask you if your personal details can be registered with a specialist centre that deals with the treatment and follow up of women with molar pregnancy. This is so that your treatment can be coordinated and provided by doctors who are experts in this field. The specialist centre is the Trophoblastic Screening and Treatment Centre at Weston Park Hospital in Sheffield.
The centre will contact you and you will be followed up by doctors there for at least six months. This follow-up involves measuring the pregnancy hormone (hCG) either through urine specimens initially at 2 weekly intervals. There are usually blood tests at the time of diagnosis and 3 months later. Fortunately, you don’t usually need to travel to Sheffield for this follow up. The centre will post you the pack for the tests and the information/ instructions you need to your home. You will need to go to either your GP surgery or local hospital to get blood tests done. You can collect the urine test at home. If your hormone levels are falling it is unlikely that you will need more treatment than the original surgery or medicine you were given.
Why is follow up important?
Even when your pregnancy hormone levels fall back to normal you will be asked not to get pregnant and to continue being monitored through Weston Park Hospital for at least six months. This may seem extremely frustrating especially if you are keen to conceive again. However, it is extremely important not to get pregnant for two reasons:
- To increase your chances of being completely cured. The programme of registration and follow up has meant that 98 to 100% of women are completely cured of molar pregnancy and it does not recur.
- To reduce the chance of the molar pregnancy progressing to gestational trophoblastic neoplasia (GTN).
What happens if my pregnancy hormone levels don’t fall?
1 in 20 women with complete molar pregnancy need to have further investigations and possibly chemotherapy.
What is gestational trophoblastic neoplasia (GTN)?
GTN is a rare form of cancer. It has a cure rate of over 99% if it develops after a molar pregnancy. It occurs when some of the molar pregnancy tissue persists. It is usually diagnosed if your HCG levels do not return to normal which is why follow-up is so important. It can also occur after a miscarriage or after a normal birth but this is much rarer.
If you have persistent irregular bleeding after a miscarriage or birth you should perform a pregnancy test and see your GP if it is positive.
If you are diagnosed with GTN you can get more information from Weston Park Hospital, Sheffield.
When is it safe to start having sex again?
Medically, it is safe to have sex once any vaginal bleeding and discharge have stopped. However, if you are feeling tired and/ or you are still sore or in pain you may want to wait longer. Emotionally, you may also want to wait longer.
What contraception can you use?
While you are being followed up after a diagnosis of molar pregnancy you should use barrier contraception such as condoms or femdoms until your pregnancy hormone levels are normal. You can also use the combined oral contraceptive pill.
What effect does this have on future pregnancies?
Having a molar pregnancy does not affect your chances of having another baby. You should not aim to get pregnant until your follow-up programme is complete. For most women
However, it is extremely important that you do not get pregnant again until the follow up is complete as this will increase the chance of a recurrence -this is at least six months. Effective contraception needs to be used until then.
The risk of a molar pregnancy happening again is 1 in 250 that means that if 250 women had a molar pregnancy, only one of them would go on to have another one. If you have a complete molar pregnancy the chance of recurrence is 1 in 80.
It is important to take the advice given to you by the specialist centre.
Emotional recovery
Everyone deals differently following a molar pregnancy. You may feel some of the following:
• Upset or fear over the experience
• Worry about getting pregnant again
• Grief or shock
• Guilt or blame over what has happened
Please talk about these concerns to the doctors and nurses on the gynaecology assessment and treatment unit, your GP or the Miscarriage Association.
Further information and support
Sheffield Trophoblastic Disease Centre, Weston Park Hospital, Sheffield, S10 2SJ.
Telephone: 0114 226 5205