Purpose of investigation: This report describes a case of urinary tract infection (UTI) due to Shigella sonnei during pregnancy. Methods: A 31-year-old pregnant woman was admitted complaining of left-flank tenderness, dysuria, and fever. Results: Following examination, significant laboratory data were collected including increased leukocyte count (10,800/ul with 86% neutrophils) and Creactive protein (9.6 mg/dl). Urinalysis revealed 30 to 50 leukocytes per high power field while from the quantitative urine culture Shigella sonnei was recovered after 24 h incubation at 37°C. After a two-week course with 750 mg cefuroxime every 8 h, the patient experienced gradual resolution of all symptoms and urinary cultures were negative two weeks and one month, respectively, after completing the therapy. The gestational course was uneventful and the patient delivered a healthy baby girl at term. Conclusion: Shigella sonnei can be responsible for UTI during pregnancy even when no predisposing factors or an apparent source of infection can be identified.