Accuracy of the cockcroft–gault equation in estimating glomerular filtration rate in normal pregnant ladies at different gestations

Abstract

Background Pregnancy induces substantial renal physiological changes, including glomerular hyperfiltration and decreased serum creatinine concentrations. Creatinine-based estimation equations developed for nonpregnant populations may inaccurately reflect pregnancy-related hyperfiltration. This study evaluated the accuracy of Cockcroft–Gault-derived estimated glomerular filtration rate (eGFR) against measured creatinine clearance (CrCl) across pregnancy trimesters in women with normal kidney function. Patients and methods This cross-sectional study was conducted at Mansoura University Hospital and Ministry of Health hospitals in Egypt between May and October 2024. A total of 30 pregnant women (10 per trimester) with singleton pregnancies and no comorbidities were enrolled. Twenty-four-hour CrCl was compared with Cockcroft–Gault-derived eGFR. Statistical analyses included Paired t -tests, Wilcoxon signed-rank tests, and Bland–Altman analysis. Results The mean maternal age was 28.7 ± 6.41 years, with a mean BMI of 32.7 ± 5.07 kg/m 2 . Mean measured CrCl was 121 ± 12.6 ml/min, whereas mean eGFR was substantially higher at 212 ± 49.1 ml/min/1.73 m 2 . Significant overestimation was observed across all trimesters: first-trimester bias 73.8 ± 60.21 ml/min ( P =0.004), second-trimester bias 98.8 ± 58 ml/min ( P <0.001), and third-trimester bias 99.45 ± 43.1 ml/min ( P <0.001). Bland–Altman analysis demonstrated poor agreement with wide limits and proportional bias, particularly at higher GFR values. Conclusion The Cockcroft–Gault equation systematically overestimates GFR throughout pregnancy, with the magnitude of overestimation increasing from early to late gestation. Clinicians should exercise caution when using this equation in pregnant women. Twenty-four-hour CrCl measurement remains preferable for accurate assessment of renal function during pregnancy, particularly for medication dosing adjustments.