A case of hyponatraemia cured by delivery

Hyponatraemia is the most common electrolyte abnormality in pregnancy. In severe cases, it can result in significant maternal and fetal morbidity and mortality. The prevalence of hyponatraemia in pregnancy has been estimated to be 0.27%, with the major causes being hyperemesis gravidarum in the first half and preeclampsia in the latter half of pregnancy. Pregnancy-specific causes of the syndrome of inappropriate antidiuretic hormone release include preeclampsia, prolonged labour, caesarean section, postpartum haemorrhage, cortisol deficiency and oxytocin. Excess water intake can also lead to hyponatraemia during labour, a period of excess antidiuretic hormone secretion. A case of idiopathic severe hyponatraemia with biochemistry consistent with inappropriate antidiuretic hormone secretion progressing during the third trimester with rapid spontaneous resolution post-partum is presented.