The appearance of polyhydramnios and dilated bowel loops on prenatal sonographic examination usually implies mechanical obstruction. The prognosis is variable, depending on the etiology. Congenital pseudo-obstruction, a potentially lethal disease, comprises a group of disorders characterized by intestinal obstruction in the absence of an anatomic lesion. This report focuses on the prenatal diagnosis of intestinal pseudo-obstruction, and two cases of transient congenital intestinal pseudo-obstruction in one family are described. In both, the prenatal sonographic presentation was of small bowel obstruction. In one case there was postnatal suspicion of neurogenic bladder, and in the other there was unilateral hydronephrosis. The sonographic appearance of intestinal pseudo-obstruction is similar to that of mechanical obstruction. The clues to the prenatal diagnosis of pseudo-obstruction include associated urinary tract abnormalities and a family history of pseudo-obstruction. Copyright © 2007 ISUOG. Published by John Wiley & Sons, Ltd.