A 30-year-old primigravida presented with isolated left sixth nerve palsy at 38 weeks gestation. Her MRI showed a lesion consistent with central pontine myelinolysis (CPM). Extensive investigations did not reveal any secondary cause for the CPM. She recovered spontaneously in 2 weeks with complete resolution of her MRI changes. To our knowledge, this is the first report of CPM occurring in third trimester in the absence of identifiable secondary causes and of CPM presenting as an isolated sixth nerve palsy. We discuss the reported causes of CPM in pregnancy, possible pathophysiologic mechanisms involved and the anatomic basis of the unique clinical presentation of sixth nerve palsy in our case.