High dietary protein intake is known to increase glomerular filtration rate in the nonpregnant state. The effects of dietary protein on renal function in human pregnancy are not well known. We studied 392 patients with singleton uncomplicated pregnancies at gestational ages of 7-40 weeks. Creatinine clearance was correlated with protein intake estimated from 24-hour dietary recall during the same period. Creatinine clearances were significantly higher when dietary protein was more than 50 g than when it was less than 50 g (P<.005). The short- or long-term significance of this finding is unclear