Urinary nitrogen excretion as related to dietary protein in pregnant women.

The amount of urea in the urine acutely decreases when dietary protein is restricted. This change in urinary urea nitrogen can be represented satisfactorily by the urea nitrogen/total nitrogen (UN/TN) ratio or the UN/creatinine nitrogen (UN/CN) ratio. These determinations are apparently effective tools for simply and objectively describing the recent protein intake of pregnant women.