Association between the serum uric acid-to-creatinine ratio index and the risk of preeclampsia in advanced maternal age pregnant women: a retrospective cohort study

Background Advanced maternal age is associated with an increased risk of preeclampsia;however, reliable and easily accessible biomarkers for early risk stratification remain limited. The serum uric acid–to–creatinine ratio (SUA/sCr) has been proposed as an indicator of systemic oxidative stress, yet evidence regarding its association with preeclampsia remains limited. This study aimed to examine the association between SUA/sCr levels and the risk of preeclampsia among women of advanced maternal age. Methods a total of 2,296 pregnant women aged ≥35 years were included in this retrospective cohort study. Multivariable logistic regression models were applied to evaluate the association between SUA/sCr and preeclampsia, with odds ratios (ORs) and 95% confidence intervals (CIs) reported. Restricted cubic spline regression was used to assess potential dose-response and non-linear relationships, and subgroup analyses were conducted to explore potential effect modification. Results Preeclampsia occurred in 14.29% of the participants. After multivariable adjustment,each standard deviation increase in SUA/sCr was associated with a higher risk of preeclampsia(OR = 1.29; 95% CI: 1.13–1.47; P = 0.0001). Restricted cubic splines suggested no strong evidence of nonlinearity ( P = 0.354), while a two-piecewise model indicated a suggestive change-point, with a suggested inflection point at an SUA/sCr value of approximately 8.18 (95% CI: 7.60–8.55);However, the threshold effect did not reach conventional statistical significance. Below this value, SUA/sCr was positively associated with preeclampsia risk, whereas no significant association was observed above it. The calculated E-value (1.73) indicated moderate robustness to unmeasured confounding. In subgroup analyses, the association differed by proteinuria status ( P for interaction = 0.0146), which should be interpreted cautiously and warrants external validation. Conclusion Higher SUA/sCr levels in early pregnancy were associated with an increased risk of preeclampsia among women of advanced maternal age. These findings suggest that SUA/sCr may serve as a potential risk indicator in this population; however, the observed non-linear relationship should be interpreted cautiously and warrants further prospective validation.