Pre-eclampsia is a condition that only occurs in women who are at least 20 weeks pregnant, though it may occur a short while after childbirth. It is thought that some form of pre-eclampsia will occur in as many as 10% of all pregnancies, though severe pre-eclampsia affects only 0.5%. The condition is characterised by high blood pressure and protein in the urine, and is due to a reduction of maternal blood supply to the placenta [The placenta is an organ that develops alongside the foetus and allows an exchange of nutrients, gases and waste products between blood from the mother and blood from the foetus. ] . Other symptoms, ranging from excessive blood clotting to kidney or liver damage, may occur in the mother if the placenta is damaged by the lack of blood supply. Eclampsia is the name given to a state of convulsions, altered consciousness and eventually coma that may occur following pre-eclampsia, or in some cases entirely out of the blue ['Eclampsia' comes from the Greek for 'like a flash'. ] . Severe pre-eclampsia and eclampsia are potentially life-threatening, and the only cure is to deliver the foetus and placenta.