What is a Molar Pregnancy?

Molar pregnancies are quite rare, happening with roughly 1 case for every 600 pregnancies in the UK.

What is a Molar Pregnancy?

A molar pregnancy is one of a number of different conditions that are called gestational trophoblastic disease (GTD). It is a rare condition that can develop during pregnancy.

GTD -

• Gestational means pregnancy

• Trophoblasts are cells in the placenta

How does a Molar Pregnancy develop?

When a molar pregnancy arises a problem occurs at the time of conception, when the egg and sperm join together that results in the formation of cells that grow very rapidly but are unable to form the placenta and foetus of a normal pregnancy.

• Complete

In a complete molar pregnancy the genetic material is just from the father as the original nucleus containing the mother’s genetic material is lost at the time of conception or whilst the egg is developing in the ovary. Complete molar pregnancies form a mass of rapidly growing cells but do not contain a foetus and can not develop into a baby. After diagnosis and evacuation there is about a 10-15% chance of needing further treatment.

• Partial molar pregnancies.

In a partial molar pregnancy there is genetic material from both the father and the mother but an imbalance as there two sets from the father. In a partial molar pregnancy there can be a foetus visible on an early ultrasound, but it is always abnormal and cannot survive. After the evacuation, most partial molar pregnancies do not require any additional treatment as in more than 99% any of the residual cells just die away over the following weeks.

How is a Molar Pregnancy found?

Most complete molar pregnancies are diagnosed at the first ultrasound scan. In a complete molar pregnancy the scan shows a mass of cells without the presence of a foetus. In a partial mole an abnormal non-viable foetus and placenta may be seen.

What happens after Diagnosis?

Once a molar pregnancy is confirmed the first step is to evacuate the cells from the uterus. This is normally done by a small surgical procedure called a Dilatation and Curettage (D & C) but occasionally, particularly with a partial molar pregnancy, this is done with the use of tablets that make the uterus contract and expel the cells. The tissue removed at the time of the evacuation has a characteristic appearance, particularly in a complete mole and is often described as looking like a bunch of grapes. After the initial evacuation all women with a molar pregnancy should be registered in a follow-up programme that tracks what is happening to any cells that remain in the uterus and picks out those that need further treatment. All women who have a molar pregnancy are followed carefully based on repeated hCG measurements

The serum HCG level (the level of pregnancy hormone in your blood) will give a very accurate level of clearance and is usually done weekly initially. In most cases the HCG level will have achieved normality by about 8-12 weeks. The frequency of tests can then usually be reduced to every month for about 3-6 months. However, it may be necessary to attend more frequently depending on individual cases.

What is the Prognosis?

In those having had a hyatidiform, in subsequent pregnancies, the incidence is about 1 in 100. When the levels of HCG remain elevated further treatment may be needed. After the diagnosis of a complete molar pregnancy 10-15% may need further treatment. In a partial molar pregnancy 1% may need further treatment.

Further Treatment?

If medical treatment is needed, a single agent (Methotrexate) is given once a week intravenously for one hour and it is associated with minimal side effects. This treatment is usually given for 4-6 weeks. In the small number of cases needing further chemotherapy (Actinomycin D) more side effects occur.

How soon can you try to conceive again?

It is generally recommended that further pregnancies be deferred for 6 months following complete clearance of the molar disease, when HCG reaches normal. It is advised to notify your clinic of the last menstrual period as soon as the pregnancy is detected and an early scan at 8-10 weeks of gestation should be performed. Usually after delivery, one final HCG level is to be done 6-8 weeks after delivery.

For more information check out the Sheffield Group.