Invasive molar pregnancy

An invasive molar pregnancy is a type of gestational trophoblastic tumour (GTT). A molar pregnancy occurs when the fertilisation of the egg by the sperm goes wrong and leads to the growth of abnormal cells or clusters of water filled sacs inside the womb. Most molar pregnancies are benign (not cancerous). They can spread beyond the womb in some women, but are still curable. In the UK, about 1 in 700 women who become pregnant will develop a molar pregnancy. The doctor will usually see that there is a molar pregnancy on an ultrasound scan between 10 to 16 weeks into the pregnancy. The abnormal tissue cannot develop into a baby and is removed during an operation called a D and C. For many women this is all the treatment they need.

But for some women, part of the molar tissue may remain in the womb and may grow into the muscle layer. This is called an invasive molar pregnancy and the most common symptom is irregular or continued bleeding after the D and C. Invasive molar tissue can cause problems because it may spread in the bloodstream to other parts of the body, including the lungs, liver or brain.

After a molar pregnancy you are followed up very closely by your doctors and have regular blood and urine tests. These tests monitor the level of the hormone hCG (human chorionic gonadotrophin). You produce this hormone in normal pregnancy, but if you have a gestational trophoblastic tumour, such as an invasive mole, you produce it at higher levels. If your hCG level doesn’t fall after removal of the molar pregnancy, or goes up, it can mean that you have invasive disease and need further treatment.

Most women will need to have chemotherapy, although very rarely the tumour can disappear on its own (spontaneously). Chemotherapy generally works very well, and the outlook for women who have an invasive mole is very good. Most are cured of their disease and can go on to have children. There is information about chemotherapy in the gestational trophoblastic tumour section. There is also a section about follow up after a molar pregnancy, including information about contraception and future pregnancies.