Dilatation of the renoureteral cavities during pregnancy is a common occurrence, especially on the right side. Though generally asymptomatic, this dilatation can be unfrequently complicated by pain and/or urinary infections that may cause severe infectious and obstetrical complications. In such cases, drainage of the renal cavities may be indicated in very selected cases. The authors review their experience with renal bypass through an endoureteral prosthesis during pregnancy, and specify the technical aspects and the indications of this type of bypass.