Objective  To investigate the association between serum sodium and potassium levels and the risk of depressive symptoms during the second trimester of pregnancy.

Methods This study was based on a prospective birth cohort of pregnant women who registered at Chongqing Maternal and Child Health Hospital, China, between 2018 and 2020. Depressive symptoms were assessed during the second trimester using the Edinburgh Postnatal Depression Scale (EPDS). Serum sodium and potassium levels were extracted from electronic health records. Logistic regression models were used to analyze the association between serum sodium and potassium levels and the risk of depressive symptoms.

Results Among the 1429 participants, the prevalence of depressive symptoms was 52.76%. A significant negative association was observed for serum potassium, while no significant association was found between serum sodium levels and the risk of depressive symptoms. In the fully adjusted model, the highest quartile (Q4) of serum potassium was associated with a lower risk of depressive symptoms compared to the lowest quartile (Q1) (odds ratio OR = 0.715, 95% CI: 0.531 to 0.963).

Conclusion  Within the normal physiological range, serum potassium levels were associated with the risk of depressive symptoms during the second trimester of pregnancy, whereas no significant association was found for serum sodium levels.