The high incidence of foetal malformation is one of the key problems in diabetic pregnancies. More babies die from lethal malformation in these cases than from all other causes during the perinatal period in a standard population, and the proportion of perinatal deaths due to malformation rises from 9 to 20% as the total perinatal mortality is reduced. Cerebral malformation, including acrania, hydrocephalus, meningocele and monster may occur in up to 25% of such malformed infants, all leading to the death of the baby.