Hydatidiform mole is a strange abnormality of pregnancy in which the placental tissue alone develops in much the same way as it does in a blighted ovum. In hydatidiform mole, however, the chorionic villi continue to develop and multiply so that instead of producing a smaller amount of chorionic gonadotrophin they produce an excessive quantity and thus guarantee that the ‘pregnancy’ continues.
A pregnancy test will be positive even when the urine is diluted more than 200 times which gives some indication of the amount of hormone being produced by the hydatidiform mole. The chorionic villi gradually become distended and cystic so that the whole uterus is filled with a mass of tissue which resembles a bunch of small grapes.
Hydatidiform mole is a rare complication of pregnancy in Britain. All the signs and symptoms of early pregnancy are present and may frequently be rather excessive. It may be first suspected at about the 14th or 16th week of pregnancy when the uterus is much larger than it should be. This rapid enlargement may also cause intermittent vaginal bleeding.
The diagnosis may be very difficult, especially in the early stages of pregnancy although the continuous intermittent loss of a small amount of bright or darkish blood may arouse suspicion. No foetal movements will be felt and a foetal heart will not be heard, neither will an X-ray demonstrate any foetal skeleton. Diagnosis is usually confirmed by repeated findings of a positive pregnancy test when the urine is diluted more than 200 times. The findings on ultrasound scanning are diagnostic.
A hydatidiform mole must be removed from the uterus and this is usually done by dilatation of the cervix followed by curettage or aspiration while the woman is anaesthetized. Alternatively she may be given syntocinon, or a similar hormone, such as prostaglandins, to make the uterus contract sufficiently to expel its contents after which curettage is performed to ensure that the uterus is completely empty.