What happens to creatinine levels by mid-pregnancy?

• A. Creatinine increases about 0.3 mg/dL
• B. Creatinine decreases about 0.3 mg/dL
• C. Creatinine remains unchanged
• D. Creatinine doubles

Answer: (A)

In pregnancy, the kidneys work harder: renal blood flow and the glomerular filtration rate rise, so creatinine is cleared more efficiently. Because of this increased clearance (and some dilution from expanded plasma volume), serum creatinine typically falls by mid-pregnancy. A decrease on the order of about 0.3 mg/dL from baseline is a common, expected change. If creatinine were to rise, that would suggest something affecting kidney function, which is not the normal mid-pregnancy pattern.