Urea kinetics in normal pregnancy - abstract

ABSTRACT

There is need for an increase in protein deposition during pregnancy. However, the requirement for dietary protein and also the pattern of the increased needs throughout gestation remains unclear. Based on nitrogen balance studies, a single value for the daily allowance throughout pregnancy has been proposed by various expert committees with recognition of the inherent limitations of this recommendation. Urea kinetics which represent a sensitive marker for the adequacy of dietary protein was measured in trimesters 1, 2, and 3 in 13 healthy pregnant women and in 8 healthy non-pregnant women (controls) using the prime/intermittent intravenous presentation of 15N 15N urea. The results are given in a Table. P/I indicates that although more protein was consumed in pregnancy compared to the controls, less was oxidised. Also E/I was significantly less at all stages of pregnancy. T, that portion of P that was salvaged and not excreted, was highest in the 1st trimester. It contributes to the nitrogen available for metabolism and is 20 - 30 per cent of P when protein intake is adequate. T+I, the total nitrogen available for metabolism was highest in the 2nd trimester. The results suggest that the demand for nitrogen is not constant throughout pregnancy and that there is an increased demand in early pregnancy. In particular, this increase was not met by the quantity and/or quality of the deitary intake in the first trimester. These changes in nitrogen metabolism have important implications for making recommendations for dietary protein intake during pregnancy (AU)