Introduction:
Mild hyponatremia is common during pregnancy due to physiologic changes of pregnancy [1]. During pregnancy, physiologic changes occur in volume- and osmoregulation that effect plasma osmolality and sodium concentration. In healthy pregnancy, the average plasma-osmolality is decreased by 5-10 mmol and the sodium concentration is decreased by 5 mmol/l [2]. Typically, this kind of hyponatremia is asymptomatic and these changes resolve on their own after delivery. The cause of hyponatremia in pregnancy is mainly due to water retention following neuro-hormonal changes during pregnancy. It has been stated that high levels of estrogen and progesterone in pregnancy can exacerbate the neurological symptoms of hyponatremia as they inhibit the maternal brain’s sodium pump [3]. These changes result in a decrease in osmolality, and therefore, the threshold for the hypothalamic secretion of ADH and the threshold for thirst is reset to a lower plasma osmolality level, creating a hypo-osmolar state characteristic of pregnancy.
Symptoms of hyponatremia can vary depending on severity. It can be asymptomatic or present with headaches, nausea, dizziness, seizures, and even death. Mild hyponatremia is mostly overlooked as it presents with nausea and weakness, overlapping with symptoms of pregnancy. As sodium and water diffuse across the placenta, the fetus is also at risk of hyponatremia. This can be associated with respiratory distress, feeding problems, and seizures showing that a hyponatremia baby was delivered [1].