Causes of Polyhydramnios

• Idiopathic: About 60% of cases.
• Maternal causes: Diabetes (increases fetal urination), infection (CMV, toxoplasmosis).
• Placental causes: Placental tumors (e.g., chorioangioma) or vascular malformations.
• Fetal causes
  • Central nervous system: Decreased swallowing.
  • Gastrointestinal: Atresias at various levels.
  • Cardiovascular: Anemia leading to hyperdynamic circulation and increased fetal urination.
  • Neoplastic: Thoracic lesions with mass effect on esophagus. Renal tumors (mesoblastic nephroma, congenital Wilms). Sacrococcygeal teratoma. Large ovarian cyst.
  • Chromosomal: For example, trisomy 21, 18.