Establishment of trimester-specific reference intervals of renal function tests and their predictive values in pregnant complications and perinatal outcomes: A population-based cohort study

Objectives: In this study, we aimed to establish the trimester-specific RIs of renal function tests (RFTs) in singleton pregnant women and investigate the associations between adverse perinatal outcomes and abnormal renal function laboratory results.Methods: The results of RFTs and the associated medical records were retrieved from 16489 singleton pregnant women who underwent first-and third-trimester prenatal screening and gave a live birth at out institute between August 2018 and December 2019. The RFTs were performed on the automated immunochemistry platform ARCHITECT ci16200 (Abbott Laboratories Ltd, Abbott Park, Illinois, US) in the clinical laboratory of our institute. The nonparametric 2.5th-97.5th percentile intervals and the indirect Hoffmann methods were used to define the trimester-specific RIs. The associations between abnormal RFTs and adverse pregnancy outcomes was assessed statistically by logistic regression.Results: There was no significant difference between the direct observational and the indirect Hoffmann methods in establishing RIs of RFTs. Compared with RFTs in the first trimester, the concentrations of serum BUN and Crea were slightly decreased (p < 0.001), and the serum UA and Cys C levels were significantly elevated in the third trimester (p < 0.001). In the logistic regression analysis, high concentrations of UA, Crea, and Cys C in late pregnancy were associated with an increased risk of postpartum hemorrhage. Meanwhile, early pregnancy UA was associated with a modestly increased risk of GDM, GH, and PE.Conclusion: It is necessary to establish trimester-specific RIs for RFTs, in order to appropriately interpret laboratory results and to identify women with high risks of developing various adverse outcomes.