PATHOPHYSIOLOGY OF POLYHYDRAMNIOS

1. Increased Production of Amniotic Fluid.
• Physiologic.
• Increased renal solute load (e.g. hyperglycemia).
• Increased renal blood flow (hypervolemia, twin-twin transfusion).
• Absent ADH/ arginine vasopressin production (e.g. diabetes insipidus in severe anencephaly).
• Increased extrarenal sources of fluid.
• CNS (e.g. neural tube defect).
• Placental / fetal hemangioma.
• Excess saliva production.
2. Decreased Elimination of Amniotic Fluid.
• Impaired swallowing (e.g. anencephaly).
• Upper GI tract obstruction (intrinsic or extrinsic).

REFERENCES

1. Manning FA. In: Fetal medicine. Principles and practice. Appleton and Lange, Norwalk, Connecticut 1995:206-216.