From Immersion to Seizure: A Novel Case of Water Intoxication Complicating a Water Birth.

Water immersion birth (WIB) is increasingly used for pain relief during labour, offering high maternal satisfaction and reduced need for epidural analgesia. However, its potential complications, particularly regarding fluid and electrolyte balance, remain underexplored. We report a case of a healthy 33-year-old woman who developed a generalized tonic-clonic seizure two hours after delivering via WIB. Her antenatal course and labour progression were clinically normal; however, she experienced retention of urine and continued fluid intake during her four hours of immersion. Post-seizure investigations revealed serum sodium measured at 124 mmol/L indicated severe hyponatremia and metabolic acidosis. Neurological imaging and EEG were unremarkable. With supportive care and correction of sodium levels, her condition stabilized. This case highlights the possibility of dilutional hyponatremia associated with prolonged WIB, especially when coupled with high fluid intake and delayed urine output. Water immersion may promote vasopressin release, impair free water clearance, and precipitate acute symptomatic hyponatremia. Although WIB is generally safe, prolonged immersion and unmonitored fluid intake may increase the risk of water intoxication. Vigilant monitoring of fluid balance is essential to prevent complications. In selected cases, serum sodium monitoring should be considered, particularly with prolonged immersion or abnormal urinary output.