Medical Q&As

Hydatidiform mole - please explain?

I would like some information on hydatidiform mole during pregnancy. Why does it happen? What aftercare is involved and are there dangers associated with future pregnancies?

Hydatidiform mole is also known as a hydatid mole or molar pregnancy. The term is derived from the Greek word hydatis, which means droplet of water and is applied to this condition because of the appearance of the placenta, which looks like a mass of droplets. The term mole is used because the mass of tissue appears to burrow mole-like into the wall of the womb. The cause of hydatidiform mole is not fully understood but does involve a breakdown in the joining of chromosome material at the time of fertilisation. The mole largely consists of placental tissue and usually there is no foetal tissue present. There is a variant of the condition known as a partial mole where the placental changes are less marked and a foetus is present however, it does not survive. The majority of hydatididform moles are benign but in approximately 10% of cases they can become invasive and intrude into the wall of the womb giving rise to haemorrhage and other complications. In 2% of cases the mole can evolve into choriocarcinoma, which is a highly malignant growth that can spread throughout the body. Despite the highly malignant nature of choriocarcinoma most women respond extremely well to treatment, which can include aggressive chemotherapy. Women with a molar pregnancy are typically large for dates, with no signs of foetal life yet have a persistently positive pregnancy test. They are often troubled with hyperemesis gravidarum, which is a very unpleasant condition that causes recurrent nausea and vomiting. In some cases the condition of molar pregnancy comes to light as the women presents in the act of spontaneously expelling the mass of tissue. Otherwise the mole is expelled in a procedure similar to artificial induction of labour. The woman is followed up with regular pregnancy tests for some time after the mole has been eliminated. If molar tissue is still present the pregnancy test continues to be positive despite the termination of the pregnancy. In such cases chemotherapy may be indicated to eliminate the persistent tissue. On the other hand a negative pregnancy test confirms that treatment has been successful. Women are usually advised not to become pregnant for at least 9 months after a molar pregnancy in order to eliminate any confusion about the significance of a positive pregnancy test. The risk of recurrence of hydatidiform mole in subsequent pregnancies is low. It does not have implications for future pregnancy except in the case of choriocarcinoma, which may require hysterectomy.