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Creatinine Clearance Calculator in Pregnancy

Measured timed urine creatinine clearance with optional BSA correction, collection adequacy check, and estimate-only Cockcroft-Gault comparison.

Instructions and clinical scope

Preferred approach in pregnancy: use a measured timed urine creatinine clearance when quantitative creatinine clearance is needed. Standard eGFR equations such as CKD-EPI and MDRD are not valid for clinical renal-function assessment in pregnancy. Cockcroft-Gault may provide a rough estimate only when a timed urine collection is unavailable, but measured creatinine clearance is preferred.

Measured timed urine collection

Use serum creatinine drawn near the timed collection.

Optional estimate-only comparison

Caution: Cockcroft-Gault is not a pregnancy-specific equation. Use it only when a timed urine collection is unavailable or as a rough comparison. Do not substitute CKD-EPI or MDRD eGFR for renal-function assessment in pregnancy.
Suggested wording

In pregnancy, renal function should generally be assessed using serum creatinine and, when creatinine clearance is required, a measured urine creatinine clearance. Standard eGFR equations such as CKD-EPI and MDRD are not valid in pregnancy. Cockcroft-Gault may provide a rough estimate when a timed urine collection is not available, but measured creatinine clearance is preferred.

Equations used
CrCl (mL/min) = [Urine creatinine (mg/dL) x urine volume (mL)] / [Serum creatinine (mg/dL) x collection time (minutes)] BSA (Mosteller) = square root of ([height(cm) x weight(kg)] / 3600) BSA-corrected CrCl = measured CrCl x 1.73 / BSA 24-hour creatinine excretion = urine creatinine (mg/dL) x urine volume (mL) / 100, adjusted to 24 hours if collection time differs from 24 hours Cockcroft-Gault CrCl = [(140 - age) x weight(kg) x sex factor] / [72 x serum creatinine(mg/dL)] Female sex factor = 0.85; male sex factor = 1.0
Collection adequacy check

The calculator estimates total 24-hour urine creatinine excretion and mg/kg/day. A typical adult female range is approximately 15 to 20 mg/kg/day. Muscle mass, diet, body size, incomplete collection, over-collection, and prolonged collection time can affect this value. The adequacy flag is a quality check, not a diagnosis.

Detailed references
  1. Wiles K, Chappell L, Clark K, et al. Clinical practice guideline on pregnancy and renal disease. BMC Nephrology. 2019. Guideline statement: assess renal function in pregnancy with serum creatinine because eGFR is not valid for use in pregnancy.
  2. Gao M, Vilayur E, Ferreira D, et al. Estimating the glomerular filtration rate in pregnancy. BMC Nephrology. 2020. Serum creatinine-based eGFR formulas showed poor agreement with 24-hour urine creatinine clearance in pregnancy.
  3. Zaghloul DE, et al. Renal function estimating equations performance during pregnancy and postpartum. Obstetrics & Gynecology. 2023. CKD-EPI 2021 did not perform well in pregnancy; Cockcroft-Gault using prepregnancy or actual body weight performed best overall when 24-hour CrCl was unavailable.
  4. Cheung KL, Lafayette RA. Renal physiology of pregnancy. Advances in Chronic Kidney Disease. 2013. Review of pregnancy renal physiology, including early GFR rise of approximately 40% to 50%.
  5. Koetje PMJL, et al. Pregnancy reduces the accuracy of the estimated glomerular filtration rate based on Cockcroft-Gault and MDRD formulas. Reproductive Sciences. 2011.
  6. Ahmed SB, et al. A comparison of prediction equations for estimating glomerular filtration rate in pregnancy. Hypertension in Pregnancy. 2009.