Fetal Kidney Function Assessment (Urinary Creatinine-to-Creatinine Clearance Ratio)

What This Test Measures

The test compares creatinine levels in your urine and blood to estimate how efficiently your baby’s kidneys filter waste products. Creatinine is a waste product from muscle metabolism that builds up when kidney function declines. This ratio helps doctors assess kidney maturity and function during pregnancy.

Why It’s Done

Doctors may order this test if there are concerns about fetal kidney development, such as in cases of prenatal ultrasound findings, genetic conditions, or maternal health risks (e.g., preeclampsia). It’s also used to monitor kidney function in high-risk pregnancies.

Sample Collection Process

A healthcare provider will collect a urine sample (midstream or catheterized) and a blood sample from you. The urine is tested for creatinine concentration, while blood is analyzed for creatinine levels. Results are compared to determine the clearance ratio.

What the Results Mean

Results are typically reported as a ratio or percentage relative to expected fetal kidney function. Lower-than-expected ratios may indicate immature kidney function or potential complications. Your doctor will interpret results in the context of your pregnancy and overall health.