PURPOSE:
This systematic review explored the causes and impacts of hyponatraemia in pregnancy, particularly during labour. It examines fluid management practices, current guidance gaps, and inconsistent hydration advice. The review highlights the need for clearer education, updated recommendations, and further research to support safe, evidence-based fluid intake guidance for midwives and pregnant women.

DISCUSSION:
Hyponatraemia remains an under-recognised complication of labour with potential maternal and neonatal risks. Incidence is estimated at 5.79 per 100,000 deliveries. Evolving practices now encourage oral hydration in labour, highlighting the need for clearer fluid management guidance, monitoring, and education for women and healthcare professionals.

EVIDENCE WHERE RELEVANT:
As described in other sections

KEY MESSAGE:
This review aimed to identify and critically appraise literature on hyponatraemia in pregnancy, focusing on causes, impacts, and implications for clinical practice. Common risk factors include labour-related nausea, pain, starvation, prolonged labour, augmentation, excessive fluid intake, and a positive fluid balance over 1500mls—many of which are physiological or iatrogenic. Historical guidance, from Mendelson (1940) to GAIN (2017) and NICE (2023), reflects evolving views on fluid intake during labour. However, no randomised controlled trials compare the effects of 5% glucose versus 0.9% sodium chloride as Syntocinon diluents—highlighting a key research gap. Studies report hyponatraemia incidence ranging from 1% to 26%, with recent cases often occurring after hospital transfer, suggesting a shift in maternal behaviour and a lack of antenatal education. Despite differing views on oral fluid intake, no consensus exists on optimal fluid volumes or standardised monitoring. There is a clear need for further evidence-based guidance to support informed decision making and consent around safe fluid management. Recommendations include researching optimal Syntocinon diluents, defining safe fluid intake, initiating fluid monitoring earlier in labour, and improving antenatal education. A robust evidence base is essential to reduce hyponatraemia risk and improve maternal and neonatal outcomes. Poster session 4 (Group B)