Molar pregnancy

Gestational trophoblastic disease (GTD) is a group of rare conditions in which a tumour develops inside the uterus from abnormal tissue that forms after conception (the joining of sperm and egg). It occurs in roughly one in every 1,000 pregnancies. Most GTD is benign and does not spread, but some types can become malignant (cancerous) and spread to nearby tissues or other parts of the body.

GTD is a general term that includes the complete hydatidiform mole and the partial hydatidiform mole.

What is a molar pregnancy?#

A hydatidiform mole, or molar pregnancy, is the most common type of GTD and occurs when abnormal fertilisation takes place. There is unusual, 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 the pregnancy hormone human chorionic gonadotrophin (hCG).

There are two main forms:

• A complete hydatidiform mole forms when sperm fertilises an egg that does not contain the mother’s DNA, resulting in two sets of genes from the father. No fetus is formed.
• A partial hydatidiform mole forms when sperm fertilises a normal egg but results in two sets of DNA from the father. A fetus may start to develop, but it will be abnormal and cannot survive.

The cause of molar pregnancy is unknown#

While anyone who becomes pregnant can develop a molar pregnancy, some risk factors have been identified:

• A previous molar pregnancy or other GTD (about 1 in 100 women who have had one molar pregnancy will have another).
• Age, with the risk higher in those younger than 20 or older than 40.
• Being from some populations.
• Nutritional deficiencies, including a lack of folate, beta-carotene or protein.

Diagnosis of molar pregnancy#

A molar pregnancy can only be confirmed when the pregnancy tissue is examined under a microscope by a pathologist. This is not always possible, as tissue is not always sent to a laboratory for testing after a miscarriage or birth.

In addition to laboratory testing of pregnancy tissue, several signs may suggest a molar pregnancy:

• Vaginal bleeding not related to menstruation, or prolonged bleeding after birth.
• Ultrasound abnormalities, including an abnormal appearance of the uterine cavity or ovarian cysts.
• Abnormally high levels of hCG and its associated effects, including severe nausea (morning sickness) and high blood pressure (which can lead to pre-eclampsia).
• Signs of anaemia, including fatigue, breathlessness, dizziness and a fast heartbeat.
• Signs of an overactive thyroid (hyperthyroidism), including a fast or irregular heartbeat, shakiness, sweating, frequent bowel movements, trouble sleeping, feeling anxious or irritable, and weight loss.

Other symptoms of pregnancy, such as nausea, a growing uterus and high blood pressure, may also be present.

Treatment of molar pregnancy#

In most cases, a molar pregnancy results in a miscarriage. The pregnancy tissue is either passed spontaneously or removed with a surgical procedure, known as dilatation and curettage (D&C), suction curettage, or evacuation of the uterus.

Further treatment is required in 10 per cent of all cases#

In some cases, cells from the molar pregnancy can persist after the initial evacuation, resulting in persistent GTD (also known as gestational trophoblastic neoplasia, or GTN). There is a 15 to 25 per cent 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 within the uterus and, rarely, via the blood to other distant organs including the lungs, liver or brain.

Why monitoring is required#

By monitoring the pregnancy hormone hCG regularly, any remaining molar cells can be detected through an hCG level that does not fall or that continues to rise. This can occur at any stage during monitoring, which often needs to continue even after the hCG level returns to normal, according to the advice of your healthcare provider.

In some places, women with a hydatidiform molar pregnancy are recorded on a dedicated registry, and follow-up is monitored with support available. Elsewhere, care is usually provided by a specialist gynaecologist.

Follow-up is monitored and support is available for women with this diagnosis#

It is important to strictly avoid pregnancy until your hCG level has returned to normal, because a normal pregnancy also produces hCG and would make the monitoring blood tests ineffective. You may wish to discuss contraceptive options with your healthcare provider.

Chances of another molar pregnancy#

There is about a 1 in 100 (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 an hCG blood test to confirm the level has dropped and that you have not developed further molar disease, which would be very rare.

Where to get help#