This is a group of conditions that occur almost exclusively in pregnancy. They range
from the benign but potentially malignant hydatidiform mole (molar pregnancy) to
the frankly malignant choriocarcinoma.
So what exactly is hydatidiform mole (molar pregnancy)?
This is a condition where, following conception, the baby (embryo) does not form.
Instead, placental tissue consisting only of vesicles (sacs filled with clear fluid)
develop. The "pregnant" woman will have normal pregnancy symptoms and body changes.
In fact, in some cases, symptoms such as nausea and vomiting may be quite pronounced
and may be the first warning of something amiss. It is important to emphasize from
the outset that molar pregnancy is not a malignant condition. It appears in this
chapter for reasons explained below.
What is in a name?
Hydatidiform mole is , well, a mouthful. It comes from the Greek word hydatis (water
drop) and a Latin word mola (mass). It is a descriptive term since a typical molar
pregnancy looks like a bunch of grapes or a mass of water drops.
What about a ‘partial’ mole?
The description above refers to a ‘complete’ mole which is the commonest form. The
other variety is what is known as a ‘partial’ mole. In this, there is evidence of
embryo development but the embryo dies early. The placental tissue then undergoes
the changes described above leading inevitably to a miscarriage. It is exceedingly
rare for malignant transformation to follow a partial mole. A persistent or invasive
(non-malignant) mole can follow a partial mole and that may be treated with a course
What are the symptoms of molar pregnancy?
There may be exaggerated pregnancy symptoms. This is by no means always the case.
More commonly, the woman will have light vaginal bleeding or a brownish discharge.
More than half of such patients are found to have a uterus which feels bigger than
the apparent gestation of the pregnancy. A significant proportion, however, will
have the uterus feeling smaller than the gestation.
The diagnosis will be confirmed by an ultrasound scan which shows a characteristic
image. Very occasionally the patient will pass some vesicles.