Pre-eclampsia as a rare cause of severe hyponatraemia Isotonic sodium chloride was carefully administered. She was delivered by caesarean section at 36+1 weeks because of persistent hyponatraemia and worsening symptoms of pre-eclampsia as well as suspected acute fatty liver (ALT 1348 iu/L; NR <40 iu/L). A male infant was born (Apgar score 9 at 10 minutes)-he had mild hyponatraemia-corrected by the paediatricians. Within 24 hours of delivery, maternal hyponatraemia had improved to 133 mmol/L. This is illustrated in Figure 1. Recovery was complicated by intrapartum sepsis. She was discharged eight days later with a normal BP. Discussion Pregnancy involves physiological changes affecting water/ sodium homeostasis. However, most women with PET do not develop hyponatraemia. A recent review of 332 pregnancies complicated by PET found hyponatraemia to occur more frequently in older age and twin gestations; 2 both features were absent in our patient. However, she had features of severe pre-eclampsia, including uncontrolled hypertension and impaired hepatic function. We postulate that this was a case of hyponatraemia with hypervolaemia (excess extracellular sodium and total body water) as a result of impaired free water clearance secondary to pre-eclampsia. SIADH was discounted because of low urinary sodium and oedema. We draw attention to severe hyponatraemia as a biomarker of severe pre-eclampsia and as a rare indication for urgent delivery. This requires multidisciplinary management and continuing postpartum care to ensure favourable maternal/ neonatal outcomes.