Statistical analyses
Clinical data were extracted from medical records and entered into a computerized spreadsheet (Excel, Microsoft Japan Co., Ltd., Tokyo, Japan). EZR software (version 1.38, Saitama, Japan) was used to perform all data analyses. After using the Shapiro-Wilk test to assess the normality of the data, the Mann–Whitney U test was conducted to compare continuous variables between the two groups, and the Student’st -test was used where appropriate. The chi-square test was used to compare the following categorical variables: nulliparity, diabetes mellitus, preeclampsia, fetal growth restriction, and maternal renal dysfunction. Continuous variables included maternal age, body mass index, birth weight, gestational age at blood test, serum BUN, creatinine, and eGFR. A logistic regression model that included maternal age, body mass index, nulliparity, gestational age at blood test, twin pregnancy, diabetes mellitus, preeclampsia, and fetal growth restriction was used to develop the prediction model for maternal renal dysfunction. For each variable, odds ratios and 95% confidence intervals (95% CI) were estimated. Statistical significance set at p < 0.05 were considered statistically significant.