Vomiting and hyponatraemia in pregnancy

Abstract

A 35 year old primigravida was admitted to hospital at 18 weeks of gestation with recurrent attacks of vomiting. Her symptoms first developed in the sixth week of pregnancy, and she had been admitted three times with a provisional diagnosis of hyperemesis gravidarium. On each occasion the w o r n was hyponatraemic (plasma sodium 119-128 mmol/L), with normal plasma potassium, urea, creatinine and glucose levels. During each admission she improved with anti-emetic drugs and intravenous normal saline and was then discharged. In the eight weeks before her pregnancy, the woman had experienced anorexia, weight loss and intermittent diarrhoea. On her fourth admission she appeared well, if slightly dehydrated, had a blood pressure of 100/80 mmHg with no postural hypotension and showed discolouration of skin and mucous membranes (ascribed initially to her Portuguese ancestry). Otherwise the clinical examination was normal. She was treated with intravenous normal saline, but despite this became hypotensive (blood pressure 80/40 mmHg) and remained hyponatraemic (plasma sodium 1OP-115 mmol/L). A presumptive diagnosis of Addison’s disease was made. Blood was taken to estimate random cortisol and adrenocorticotrophic hormone levels, and she was treated with intravenous hydrocortisone. Her random serum cortisol concentration was 106 nrnoVL and adrenocorticotrophic hormone concentration was > 1500 ng/L, confinnng primary adrenal failure. The serum was strongly positive for 21-hydroxylase antibodies, suggesting auto-immune adrenalitis, the commonest cause of Addison’s disease. Glutamic acid decarboxylase, thyroid peroxidase and thyroglobulin antibodies were also positive but glucose tolerance and thyroid function were normal. Following her intravenous steroid therapy the woman was given oral hydrocortisone and fludrocortisone and subsequently her blood pressure and plasma sodium concentration returned to normal, with restoration of her wellbeing. The remainder of her pregnancy was uneventful, and she was delivered at 41 weeks of a male infant weighing 2500 g. In her