Introduction: Wernicke’s encephalopathy is an acute neuropsychiatric syndrome resulting from thiamine deficiency, which is associated with significant morbidity and mortality. The diagnosis of Wernicke’s encephalopathy is based on the clinical manifestations and rapid reversal of symptoms with thiamine. Case presentation: The authors present the case of a 25-year-old female patient at the 19th week of gestation (Gravid 1 para 0) with an unremarkable medical history who was admitted to the hospital for an areflexic flaccid tetraparesis with ataxia after persistent vomiting. The brain and spinal MRIs did not reveal any abnormalities, and the evolution was marked by an important improvement after supplementation with thiamine. Conclusion: Gayet Wernicke encephalopathy is a medical emergency. Clinical symptoms are inconstant and varied. MRI is the reference examination to confirm the diagnosis, but in 40% of cases it is strictly normal. Early thiamine administration can prevent morbidity and mortality in pregnant women.