Summary
Read the full fact sheet- Gestational trophoblastic disease (GTD) is a term covering pregnancy conditions that involve the placental tissue turning cancer-like.
- Molar pregnancy is the most common type of GTD.
- Molar pregnancy is a form of abnormal pregnancy, in which the formed placental-like tissue sometimes invades the wall of the uterus (womb).
- Molar pregnancy is usually diagnosed early in pregnancy due to bleeding, abnormal features in ultrasound scan and higher than usual levels of the pregnancy hormone, hCG.
- The cause of molar pregnancy is unknown, but risk factors include maternal age of less than 20 years or more than 40 years.
- If promptly treated, molar pregnancies are curable in 100 per cent of cases.
- Molar pregnancy can persist (known as persistent GTD), so regular check-ups are needed.
On this page
About gestational trophoblastic disease
Gestational trophoblastic disease (GTD) is a group of rare diseases in which a tumour develops inside the uterus from abnormal tissue that forms after conception (the joining of sperm and egg). In Australia, this condition occurs in one in every 1000 pregnancies. Most GTD is benign (not cancer) and does not spread, but some types can become malignant (cancer) and spread to nearby tissues or other parts of the body.
GTD is a general term that includes the following condition:
- Hydatidiform mole (also known as molar pregnancy)
- Complete hydatidiform mole
- Partial hydatidiform mole.
What is a molar pregnancy?
Hydatidiform mole, or molar pregnancy, is the most common type of GTD and occurs when abnormal fertilisation takes place. There is unusual and rapid growth of placental tissue, which becomes larger than normal and contains a number of cysts (sacs of fluid).
The overgrowing placenta produces high levels of a pregnancy hormone called human chorionic gonadotrophins (hCG), resulting in symptoms of pregnancy such as:
- nausea
- a growing uterus (womb)
- high blood pressure.
A complete hydatidiform mole forms when sperm fertilises an egg that does not contain the mother’s DNA. This results in 2 sets of genes from the father, and no fetus is formed.
A partial hydatidiform mole forms when sperm fertilises a normal egg, but results in 2 sets of DNA from the father. A fetus may start to develop but will be abnormal and cannot survive.
Risk factors for molar pregnancy
The cause of molar pregnancy is unknown.
While anyone who falls pregnant can develop a molar pregnancy, the following risk factors have been found:
- age – being younger than 20 years or older than 40 years
- Asian ethnicity
- nutrition deficiencies including lack of folate, beta-carotene or protein
- a previous molar pregnancy or other GTD (1 in 100 women who have had one molar pregnancy will have another).
Diagnosis of molar pregnancy
A molar pregnancy can only be confirmed when the pregnancy tissue is examined under a microscope by a pathologist. This not always possible as tissue is not always sent to a laboratory for testing after a miscarriage or a normal pregnancy, labour and birth.
In addition to laboratory testing of pregnancy tissue, there can be signs suggestive of a molar pregnancy:
- Vaginal bleeding – not related to menstruation, or prolonged after birth.
- Ultrasound abnormalities – including abnormal appearance of the uterine cavity or ovarian cysts.
- Abnormally high levels of the pregnancy hCG hormone and associated consequences – including severe nausea (morning sickness) and high blood pressure (which can lead to preeclampsia).
- Signs of anaemia – including fatigue, breathlessness, dizziness and a fast heartbeat.
- Signs of an overactive thyroid (hyperthyroidism) – including fast or irregular heartbeat, shakiness, sweating, frequent bowel movements, trouble sleeping, feeling anxious or irritable and weight loss.
Treatment of molar pregnancy
In most cases, a molar pregnancy would result in a miscarriage. The pregnancy tissue is either passed spontaneously, or removed with a surgical procedure. This is known as a dilatation and curettage (D&C), suction curettage or evacuation of the uterus.
Why monitoring is required after a molar pregnancy
Further treatment is required in 10 per cent of all cases. In some cases, cells from the molar pregnancy can persist (continue) after the initial evacuation, resulting in persistent GTD (also known as gestational trophoblastic neoplasia or GTN). There is a 15 to 25 percent chance of a complete mole persisting, and a 0.5 to 4 per cent chance of a partial mole persisting. If left untreated, these cells can spread into the uterus and rarely, via the blood, to other distant organs including the lungs, liver or brain.
By monitoring the pregnancy hormone hCG regularly, any remaining molar cells can be detected through a hCG level that does not fall or continues to rise. This can occur at any stage during monitoring, which often needs to continue even after the hCG level normalises, according to the advice from your healthcare provider.
In Victoria, all women with a hydatidiform molar pregnancy are registered on the Royal Women’s Hospital’s Gestational Trophoblastic Disease Registry. Follow-up is monitored and support is available for women with this diagnosis.
Queensland also has a state registry but in other states in Australia, care is usually provided by a specialist gynaecologist.
It is important to strictly avoid pregnancy until your hCG level has returned to normal, because a normal pregnancy will produce hCG and make the monitoring blood tests ineffective. You may choose to discuss contraceptive options with your healthcare provider.
Chances of another molar pregnancy in the future
There is a 1 in 100 (or one per cent) chance that you will develop another molar pregnancy. When you think you are pregnant, let your doctor know so that an early ultrasound can be arranged.
Six weeks after the birth of your baby, it is recommended to have a hCG blood test to ensure it has dropped and that you have not developed further molar disease, which would be very rare.
Where to get help
- Your GP (doctor)
- Gestational Trophoblastic Disease Registry, The Royal Women’s Hospital Tel. (03) 8345 2620, Email. GTDService@thewomens.org.au
- Sexual Health Victoria (SHV) – these services are youth friendly:
- SHV Melbourne CBD Clinic Tel. (03) 9660 4700
- SHV Box Hill Clinic Tel. (03) 9257 0100
- Free call Tel. 1800 013 952
- Cancer Council Victoria Tel. 13 11 20
- Red Nose Grief and Loss Tel. 1300 308 307 (24 hours, 7 days)
- Hydatidiform mole, Merck Manual – Consumer Version, USA.
- Hydatidiform mole, The Royal Women’s Hospital, Victoria, Australia.
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