Abnormal form of pregnancy in which a non-viable fertilised egg implants in the uterus or tube

Aetiology

• A complete mole occurs when two sperm cells fertilise an ovum that contains no genetic material (an 'empty ovum')
  • These sperm then combine genetic material, and the cells start to divide and grow
  • Complete moles have a higher risk of developing into choriocarcinoma
• Partial mole occurs when two sperm cells fertilise a normal ovum (containing genetic material) at the same time
  • The new cell now has three sets of chromosomes (it is a haploid cell)
  • The cell divides and multiplies into a tumour

Pathophysiology

• Overgrowth of placental tissue with chorionic villi swollen with fluid; giving picture of 'grape like clusters'

Clinical features

• Hyperemesis, hyperthyroidism, early onset pre-eclampsia
• Varied bleeding and occasional history of passage of 'grapelike tissue'
• Fundus > dates on abdominal palpation
• Rare cases: shortness of breath (due to embolisation to lungs) or seizures (metastasis to brain)

Investigations

• Ultrasound: 'snow storm appearance'
• Provisional diagnosis can be made by ultrasound and confirmed with histology of the mole after evacuation

Management

• Surgical procedure (uterine evacuation) and tissue sent for histology to ascertain type
• After evacuation of a hydatidiform mole, the levels of b-hCG are expected to fall and pregnancy should be avoided for 1 year
  • If they fail to drop, malignant choriocarcinoma should be suspected