Objective: Congenital diarrheal disorders (CDDs) are a group of rare diseases among which some present as inherited disorders of intestinal electrolyte transportation: congenital chloride diarrhea (CCD) and congenital sodium diarrhea (CSD) with prenatal manifestations, mainly polyhydramnios, leading to premature delivery. Affected neonates present with watery stools, sometimes mistaken as urine, leading to a misdiagnosis of Bartter syndrome. The aim of this study was to study the value of a prenatal biochemical pattern in the case of suspected CDD. Methods: We retrospectively studied 12 amniotic fluids of CDD-affected fetuses prenatally suspected and confirmed after birth. Digestive enzymes, proteins, and electrolytes were assayed and showed abnormal biochemical patterns. Results: The 12 infants (eight CCD-and four CSD-affected) were born prematurely with a normal birth weight. Electrolytes and the Bartter index were normal for all cases. Amniotic fluid enzyme patterns were abnormal: anal leakage for nine, as expected, but vomiting of bile was observed for three infants, for whom an occlusive syndrome required surgery, and thereafter severe complications appeared with a poor prognosis. Conclusion: Amniotic fluid biochemical patterns differentiate CDD from Bartter syndrome. If a vomiting bile pattern is observed, postnatal management should take into account the hypothesis of a most severe complication. Key Points What's already known about this topic? � Congenital diarrheal disorders (CDDs) are a group of rare diseases that include CCD and CSD with perinatal manifestations as polyhydramnios, premature delivery and watery stools needing adapted neonatal care What does this study add? � This study shows the value of an amniotic fluid biochemical pattern in differentiating CDD from Bartter syndrome for adapting postnatal management. A vomiting biochemical pattern is also a sign of potential most severe complication 434-Prenatal Diagnosis.