The paper describes the clinical cases of pregnant women with severe vomiting complicated by Wernicke encephalopathy (WE). The cause of this disease is vitamin B1 deficiency, which is rare in a socially prosperous population. The literature review presented by the authors shows the high (more than 20%) mortality in WE, which is associated with late diagnosis and lack of timely treatment. The clinical observations of WE in pregnant women with damage to the oculomotor and vestibular nerves are evidenced by X-ray computer studies; moreover, the disease in one of the patients ran an extremely severe course, developing to a comatose state. The authors describe in detail the classic triad of encephalopathy and the sequence of symptom occurrence and regression. Particular emphasis is laid to treatment. Emergency thiamine therapy should be initiated within 48—72 hours of first symptom onset. The authors provide literature and their own data on the need for parenteral administration of high-dose thiamine. Then patients should be prescribed vitamins B for long-term use. The prognosis of WE depends on the timing of treatment initiation. Even in this case, all the patients had long-term ataxic disorders. The perinatal prognosis was seen to be quite favorable.