When a pregnancy can turn into cancer

Posted on 5 March 2018

A molar pregnancy is a rare complication of pregnancy. Also known as a hydatidiform mole, it is characterised by abnormal growth of the cells that make up the placenta. It is diagnosed in about 1 in every 1 000 pregnancies but this figure can vary per country.

Dr MC van Aardt, a gynaecological oncologist at Mediclinic Kloof, explains more about this rare condition.

Causes of molar pregnancies

Two types of molar pregnancies can occur. A complete molar usually occurs when a sperm fertilises an egg without any genetic material, resulting in no foetus or foetal material to develop, while a partial molar pregnancy usually develops after two sperm fertilise a normal egg, resulting in an abnormal foetus that is unable to survive.

The reason why molar pregnancies occur in some women and not others is not known, however we know that they occur more often in younger woman (under 20 years old) and in women older than 35 to 40 years, says Dr Van Aardt. Women with previous molar pregnancies also have a higher risk in future pregnancies.

Treatment options

The treatment of a molar pregnancy requires surgical removal of the abnormal pregnancy. This is done under general anaesthesia by means of a procedure called suction curettage.

Can it become cancerous?

In certain cases the molar tissue can persist and grow into the muscle layer of the uterus or spread to other organs. This is called an invasive mole and occurs in between 5 and 15% of molar pregnancies. Although extremely rare, a molar pregnancy can also turn into a cancer called choriocarcinoma (<1%), which needs further oncological treatment.

In order to be assured that the molar tissue is completely gone, patients would need to have regular blood tests. We monitor the pregnancy hormone, hCG, to make sure it returns to normal and stays that way, says Dr Van Aardt. This is initially done every week until it is normal and then every month for at least six months thereafter. Patients who have hCG levels that do not decrease sufficiently or keep increasing will most likely require chemotherapy.

It is very important that woman do not fall pregnant for at least six months after a molar pregnancy. In other words, they should be on a reliable form of contraception.