INTRODUCTION: Prenatal diagnosis of bladder exstrophy is extremley rare and difficult. BACKGROUND: Due to abnormal development of the cloacal membrane there is an incomplete closure of the lower abdominal wall, absence of the anterior wall of the bladder and external exposition of the posterior wall. The pubic bones are usually separated, the umbilical cord low inserted and there is abnormal external genitalia development. CASE REPORT: At 21st week of gestation of 39-year-old multigravida multipara referred by a primary care obstetrician to high-specialised centre for a detailed ultrasound examination with a suspicion of bladder absence and inferior umbilical localisation. At 29 weeks of gestation presence of bulging mass of 2 cm, between the umbilical outlet and labia was detected. At 31 weeks of gestation previously detected structure among thighs had 3 cm diameter with lateral umbilical outlet. Major labia were prominent and minor labia were within normal limits. Between two umbilical arteries with an appropriate intraabdominal course there were no transsonic area corresponding to the urinary bladder. The newborn baby was born at term in a good condition, but with an exposed bladder of 4 cm in diameter. The urethral outlet was not visualised and the female genitals were abnormal. After a month the girl underwent primary bladder exstrophy closure. Although she suffers from recurring urinary tract infections, she is in a good general condition. CONCLUSIONS: Due to prenatal diagnostics it was possible to detect and make an initial diagnosis of severe malformation. Early diagnosis allowed to prepare parents for a newborn with a defect and teach them how to take care of the baby.