Severe hyponatremia in obstetrics: Presentations and outcome. Retrospective cohort over 10 years.

Hyponatremia in labor and the postpartum period is generally underreported. In this study we aimed to identify attributable causes of severe hyponatremia in an obstetric population and define maternal outcomes. This was a retrospective cohort study, in a single center over a period of 10 years. The study setting was an NHS maternity trust serving a multi-ethnic population in southwest London. The hospital cared for 53 649 pregnant women in the study period. All patients with severe hyponatremia in labor and immediate postpartum period from January 2011 until December 2020 were identified from the laboratory database. Individual case notes were analyzed for fluid use, use and duration of oxytocin, medical conditions, and delivery details. Severe peripartum hyponatremia was identified in 77 patients. A total of 28% of those analyzed required ITU admission for electrolyte correction, of whom 6% presented with severe neurologic symptoms, making symptoms a poor marker of severity (P = 0.051). The main association was to oxytocin and intravenous fluid infusions (80% and 86%, respectively), only one-third of patients had pre-eclampsia. Other associated medical conditions did not appear to have a significant influence on disease course nor prognosis (P = 0.359). Hyponatremia during labor can have detrimental effect on maternal outcomes. Lower threshold for testing and diligent maintenance of fluid balance charts during labor can help with primary prevention.