Electrolyte homeostasis in pregnancy: from physiological adaptations to clinical disturbances — a nephrologist’s perspective

Electrolyte homeostasis in pregnancy undergoes several important remodellings driven by systemic vasodilation, activation of neurohormonal pathways, increased glomerular filtration, altered tubular transport, and active maternal–fetal mineral exchange. These coordinated adaptations enable plasma volume expansion, mainta in utero placental perfusion, and support fetal growth, yet they narrow compensatory reserves and shift normal biochemical reference thresholds. As a result, reliance on non-pregnant laboratory norms can misclassify abnormalities, delaying recognition of clinically important disturbances. Understanding pregnancy-specific physiology is therefore essential for accurate diagnosis, monitoring, and therapeutic decision-making. This review provides an integrated nephrology-focused synthesis of normal adaptive mechanisms and disorder-specific pathophysiology across sodium–water, potassium, magnesium, and calcium balance. We summarize expected gestational changes, including the reset osmostat and AVP-mediated free-water retention causing a physiological fall in serum sodium, changes in potassium homeostasis and magnesium homeostasis, and the doubling of intestinal calcium absorption driven by increased calcitriol to meet third-trimester skeletal mineralization. We further review common clinical disorders of water and sodium, potassium, calcium, and magnesium. The review provides a comprehensive pregnancy-specific interpretation of electrolyte values, diagnostic evaluation strategies, and targeted management tailored to maternal and fetal safety aimed at improving clinical vigilance and optimizing outcomes.