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Peripartum Hyponatraemia in Pregnancy

Key points

  • Hyponatraemia occurs when the levels of sodium in the blood are abnormally low which can result in excessive levels of water in the body.
  • Little is known about hyponatraemia in pregnant women. It is thought that drinking excessive amounts of water during labour may lead to hyponatraemia but to date, too few studies have been conducted to make any definitive conclusions.

Surveillance period

1st April 2019 – 30th September 2020


There is little known about hyponatraemia in pregnancy with most knowledge limited to a growing number of case reports of woman and neonates who have had a seizure of confusion around the time of labour and delivery. These women were otherwise well so excessive drinking and oxytocin infusion diluted in 5% dextrose have been implicated in these cases[1][2][3]. Very few studies into hyponatraemia in pregnancy have been conducted so clinicians currently have a limited understanding of the disorder with regards to risk factors, outcomes and management. This study will enable co-ordinated investigation of cases nationally which will help to guide future clinical management and grounds for further research.


To use the UK Obstetric Surveillance System (UKOSS) to determine the incidence, risk factors and maternal/neonatal outcomes of per-partum hyponatraemia in obstetric patients in the UK.

Research questions

  • What is the current incidence of symptomatic peri-partum hyponatraemia in the UK?
  • What are the risk factors for the development of peri-partum hyponatraemia?
  • How is peri-partum hyponatraemia managed?
  • What are the delivery and post-partum outcomes for the mother and baby in a woman who develops a peri-partum hyponatraemia?

Case definition

Any woman with symptomatic hyponatraemia (Na <125mmol/l) in labour or in the immediate 48 hours following delivery (not caused by sepsis or pre-eclampsia) where other likely causes have been clinically excluded.

Symptoms may include any of the following – disorientation, agitation, seizures, coma and focal neurological deficits.


This study is being funded by the OAA.

Ethics committee approval

This study has been approved by the North London REC1 (Ref. Number: 10/H0717/20).

Lead investigators

Arani Pillai, Nottingham University Hospitals NHS Trust; Nuala Lucas, Northwick Park Hospital; Cathy Nelson-Piercy, Guy's and St. Thomas' Foundation Trust.

Sample Data Collection Form

UKOSS Hyponatraemia Data Collection Form


  1. ^ Valerio E, Fantinato M, Gioavannini I, Baraldi E and Chiandetti L. Severe asymptomatic maternal antepartum hyponatraemia leading to neonatal sezures: prevention is better than cure. Maternal Health, Neonataology and Perinatology 2015; 1:25.
  2. ^ Green A, Popham P. Hyponatraemia complicating vaginal delivery. IJOA, Volume 17. Issue 1. P93-94.
  3. ^ Abu Halaweh SA, Aloweidi AS, Qudaisat IY, Al-Kazaleh FA. Iatrogenic water intoxication in healthy parturient causing convulsions and fractured mandible. Saudi Med J. 2014 Feb; 35(2):192-4.

Updated: Tuesday, 17 January 2023 18:14 (v13)

Contact us

For more information about UKOSS, please view the contact details page