The case of a pregnant woman (16th week) needing an amniocentesis is reported. She rapidly developed a septic shock. Despite vaginal delivery, curettage and antibiotherapy, the patient deteriorated with the onset of an acute respiratory distress syndrome and a typical disseminated intravascular coagulation. Bacteriological data showed positive blood cultures to Escherichia coli. Amniotic liquid was positive to the same E. coli. Cultures obtained from instruments, disinfectant solutions and gel used during the procedure were negative. On the contrary, amniotic and fetal cultures were positive to E. coli and Clostridium perfringens. She died 2 days later. The incidence of septic shock following amniocentesis is very low but we report the first case of fatal sepsis and multiorgan failure, due to E. coli and C. perfringens. The mechanisms of infection are discussed: contamination from the instruments, systemic dissemination of bacteria coming from an asymptomatic intra-amniotic infection, and inoculation of the placenta with a needle passing through the bowel.