title: Hyponatremia complicating labour--rare or unrecognised? A prospective observational study.
abstract: OBJECTIVE
  The aim of this study was to investigate the occurrence of hyponatraemia following delivery, with a hypothesis that hyponatraemia has a high prevalence in labouring women.
  
  
  METHODS
  Prospective observational study.
  
  
  METHODS
  Consultant-led delivery suite in County Hospital, Kalmar, Sweden.
  
  
  METHODS
  A total of 287 pregnant women at term (37 full gestational weeks).
  
  
  METHODS
  Oral fluids were allowed during labour. Blood samples were collected on admission, after delivery, and from the umbilical artery and vein.
  
  
  METHODS
  Hyponatraemia defined as plasma sodium < or =130 mmol/l after delivery.
  
  
  RESULTS
  Hyponatraemia was found in 16 (26%) of the 61 mothers who received more than 2500 ml of fluid during labour. Two-thirds of fluids were orally ingested. Decrease in plasma sodium concentration during labour correlated with duration of labour and the total fluid volume administered. Analysis by multivariate logistic regression showed that hyponatraemia was significantly correlated with fluid volume (P < 0.001) but not with oxytocin administration or epidural analgesia. Hyponatraemia correlated significantly with prolonged second stage of labour, instrumental delivery, and emergency caesarean section for failure to progress (P = 0.002).
  
  
  CONCLUSIONS
  Hyponatraemia is not uncommon following labour. Tolerance to a water load is diminished during labour; therefore, even moderate fluid volumes may cause hyponatraemia. Women should not be encouraged to drink excessively during labour. Oral fluids, when permitted, should be recorded, and intravenous administration of hypotonic fluids should be avoided. When abundant drinking is unrecognised or intravenous fluid administration liberal, life-threatening hyponatraemia may develop. The possibility that hyponatraemia may influence uterine contractility merits further investigation.
authors.affiliation: Department of Anaesthesiology and Intensive Care, County Hospital, Kalmar, Sweden. vibekem@ltkalmar.se
authors.forename: V
authors.initials: V
authors.lastname: Moen
authors.forename: L
authors.initials: L
authors.lastname: Brudin
authors.forename: M
authors.initials: M
authors.lastname: Rundgren
authors.forename: L
authors.initials: L
authors.lastname: Irestedt
mesh_terms: D000328:Adult; D016022:Case-Control Studies; D004326:Drinking / Q000502:physiology*; D005260:Female; D006801:Humans; D007010:Hyponatremia / Q000209:etiology*; D007038:Hypotonic Solutions / Q000009:adverse effects; D007744:Obstetric Labor Complications / Q000209:etiology*; D011247:Pregnancy; D011446:Prospective Studies
chemical_list: D007038:Hypotonic Solutions