BACKGROUND: Avitaminosis can result from the acute malnutrition associated with prolonged pregnancy-related hyperemesis. Serious complications may arise from thiamine deficiency under these circumstances. CASE: We review the relevant literature and describe a case with central nervous system involvement presenting with typical manifestations of Wernicke’s encephalopathy, apparently precipitated by a combination of hyperemesis gravidarum, diabetic ketoacidosis, and intravenous glucose administration. CONCLUSION: While this life-threatening complication is rare, it is important for all who care for obstetric patients to be aware of it and alert to its development. Early recognition is critical given the need to treat affected women expeditiously to help avoid potentially fatal adverse consequences. Prophylactic thiamine supplementation should be considered in the care of gravidas with hyperemesis. BACKGROUND: Avitaminosis can result from the acute malnutrition associated with prolonged pregnancy-related hyperemesis. We review the relevant literature and describe a case with central nervous system involvement presenting with typical manifestations of Wernicke’s encephalopathy, apparently precipitated by a combination of hyperemesis gravidarum, diabetic ketoacidosis, and intravenous glucose administration. CONCLUSION: While this life-threatening complication is rare, it is important for all who care for obstetric patients to be aware of it and alert to its development Early recognition is critical given the need to treat affected women expeditiously to help avoid potentially fatal adverse consequences. Prophylactic thiamine supplementation should be considered in the care of gravidas with hyperemesis.