Pregnancy outcomes in women with hyponatraemia and preeclampsia: Case series and literature review.

Objectives: To determine the prevalence, clinical course, complications and management of preeclampsia complicated by hyponatraemia.

Study Design: A ten year retrospective audit of women delivering at a tertiary referral hospital with preeclampsia complicated by hyponatraemia (defined as serum sodium < 130 mmol/L).

Main Outcome Measures: The prevalence, time to delivery, complications, treatment and time to recovery of hyponatraemia in women with preeclampsia associated with hyponatraemia.

Results: There were 129 cases of preeclampsia associated with hyponatraemia, representing 9% of women with preeclampsia, and 0.27% of deliveries overall. Hyponatraemia was associated with a significant rate of complications of preeclampsia; acute kidney injury in 34.1%, HELLP syndrome in 17.1%, fetal growth restriction in 36.4%, stillbirth in 2.3%, the use of magnesium sulphate in 44.2%, and postpartum maternal admission to an intensive care unit in 28.7%. Moderate/severe hyponatraemia was associated with greater risk of acute kidney injury, fetal growth restriction and post-partum maternal admission to an intensive care unit than mild hyponatraemia. Urgent delivery was required in 71% of women for either obstetric or fetal indications within 24 h of diagnosis of moderate/severe hyponatraemia. In almost all cases, hyponatraemia rapidly resolved postpartum without requirement for fluid restriction or intravenous saline.

Conclusions: Hyponatraemia should be regarded as a marker of severity in the setting of preeclampsia, and in the absence of an alternative cause may be an indication for expedited delivery. Hyponatraemia typically recovers rapidly following delivery without the need for specific therapy.