The antenatal investigation of an obstetric patient with a history of myotonia is described. The smooth and striated muscle dysfunction in myotonic dystrophy renders these patients, as a group, liable to surgical correction and exposure to anaesthesia. A caesarean section is reported to illustrate the preferred timing of diagnosis and peripartum management. While regional anaesthesia is preferred, myotonic dystrophy is not a contraindication to general anaesthesia, provided risks are anticipated and steps taken to minimize complications.