Pregnancy reduces the accuracy of the estimated glomerular filtration rate based on Cockroft-Gault and MDRD formulas.

OBJECTIVE

This study aims to determine the effect of pregnancy on the accuracy of 3 commonly used methods to estimate glomerular filtration rate ([GFR] creatinine clearance, the Cockroft-Gault, and modification of diet in renal disease [MDRD] formulas) using the inulin clearance as a reference.

DESIGN

Longitudinal study design.

SETTING

University hospital.

POPULATION

A total of 44 parous nonsmoking Caucasian women. They had a history of uneventful pregnancy (n = 9), preeclampsia (n = 27), and intrauterine fetal demise (n = 8).

METHODS

Measurements were performed both in pre-pregnancy and early pregnancy (8 weeks of gestation) and included inulin infusion, blood pressure, and 24-hour urinary and serum creatinine. Agreement between methods to estimate GFR was assessed by the Bland and Altman method.

MAIN OUTCOME MEASURES

GFR estimated by inulin and creatinine clearances and the Cockroft-Gault and MDRD formulas.

RESULTS

During early pregnancy, the GFR measured by inulin increased 32% compared with the pre-pregnant value (from 115 ± 18 to 150 ± 23 mL/min·1.73 m(-2)), whilst the GFR measured by the indirect methods only increased 20%. The observed bias and limits of agreements are larger in early pregnancy relative to the pre-pregnant state for all 3 methods.

CONCLUSION

The renal hyperfiltration during pregnancy decreases further the accuracy of the creatinine clearance and the Cockroft-Gault and MDRD formulas to estimate GFR.