Key result
High-normal potassium and sodium in mid-late pregnancy linked to higher adverse pregnancy outcome risks.
Why the study?
Are trimester-specific maternal serum potassium and sodium levels associated with hypertensive disorders of pregnancy and major adverse pregnancy outcomes?
Cohort (n=71,351)
Yes
Are trimester-specific maternal serum potassium and sodium levels associated with hypertensive disorders of pregnancy and major adverse pregnancy outcomes?
High-normal potassium (>4.10 mmol/L) and high-normal natremia (>141 mmol/L) in mid-late pregnancy may increase the risk of adverse pregnancy outcomes, suggesting a need for trimester-specific electrolyte monitoring.
Background & Aims Maternal electrolyte levels influence blood pressure and fetal growth. Physiologic plasma volume expansion shifts maternal potassium and sodium levels, but exact optimal ranges remain uncertain. We explored trimester-specific potassium and sodium levels and their links to hypertensive disorders of pregnancy (HDP) and major adverse pregnancy outcomes (APOs), including preterm birth (PTB), small-for-gestational-age (SGA), gestational diabetes mellitus, large-for-gestational-age, and perinatal death. Methods Data were obtained from two cohorts of singleton pregnancies in China (n=71,351). Maternal serum potassium and sodium levels were measured in the first (n=5,597), second (n=15,912), and third (n=64,590) trimesters. Restricted cubic spline models were used to model nonlinear associations with APO risk, and logistic regression estimated adjusted odds ratios (ORs) for APOs across electrolyte ranges. Results No clear dose-response pattern for potassium and sodium was observed in the first trimester. During the second trimester, high-normal potassium (>4.10 mmol/L; particularly relevant for preterm PE) and sodium <137 mmol/L were associated with increased risks of PE, SGA, and PTB, whereas potassium <3.70 mmol/L and sodium >141 mmol/L were associated with higher risks of perinatal death and PTB. These potassium-APO associations persisted into the third trimester, whereas sodium showed no consistent dose–response pattern during this period. Conclusion Although standard lower reference limits for potassium (3.5 mmol/L) and sodium (135 mmol/L) remain generally applicable during pregnancy, high-normal kalemia (> 4.10 mmol/L) and high-normal natremia (> 141 mmol/L) in mid-late pregnancy may increase APO risks. These findings highlight the need for closer, trimester-specific electrolyte monitoring to inform individualized clinical management and improve maternal-fetal outcomes.Graphical Abstract
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Xu et al. (2025) conducted a cohort in Singleton pregnancies (n=71,351). Maternal serum potassium and sodium levels vs. Standard reference limits was evaluated on Hypertensive disorders of pregnancy and major adverse pregnancy outcomes. High-normal potassium (>4.10 mmol/L) and sodium (>141 mmol/L) in mid-late pregnancy were associated with increased risks of major adverse pregnancy outcomes.
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