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Changes in Serum Uric Acid Concentrations during Normal Pregnancy

1984; Lippincott Williams & Wilkins; Volume: 39; Issue: 9 Linguagem: Inglês

10.1097/00006254-198409000-00004

1533-9866

T. Lind, Krista Godfrey, H Otun, P. R. Philips,

Electrolyte and hormonal disorders

During pregnancy, progressive maternal adaptations occur, and many biochemical measurements deviate from the normal range for males and nonpregnant females. Laboratory ranges specific to pregnancy need to be defined. Ideally, they would be determined in healthy women having uncomplicated pregnancies resulting in the birth of live, healthy children, but such data are scarce. The present paper describes the changes in serum uric acid concentrations throughout normal pregnancy and reports two clinically important aspects. First, the values decrease significantly below nonpregnant levels by 8 weeks of gestation. Second, uric acid concentrations in serum are not only increased above nonpregnant values by term in many women, but they remain elevated for as long as 12 weeks after delivery. Such postpartum values, therefore, should not be used as representative of nonpregnant concentrations. Thirty-one healthy women, with a mean age of 28 years (range, 23–37 years), were included in the study. Blood samples were taken at approximately 4, 8, 12, 16, 24, 32, 36, and 38 weeks of gestation and 12 weeks postpartum. There was a wide range of uric acid concentrations before, during, and after pregnancy. Two general points emerged: 1) the mean values decreased during the first trimester, remained at this lower level until about 24 weeks of gestation, and increased thereafter; 2) the mean concentration 12 weeks after delivery was higher than that before conception. This pattern was followed closely by individuals. There was also a clear tendency for subjects to retain their positions in the spectrum of uric acid values throughout pregnancy, which indicates that women who had high concentrations before pregnancy tended to remain in the upper range of values through pregnancy. Those with lower values before pregnancy tended to remain in that category. It appeared that before conception the wide range of observed concentrations resulted more from genuine differences among patients than from variations in uric acid values within patients from occasion to occasion. In those patients in whom 24-hour creatinine clearances were being determined, the reabsorption of uric acid was measured also. The amount reabsorbed decreased by 8 weeks of gestation, remained at the reduced level until about 24 weeks, and increased thereafter to such an extent that, by term, the amount reabsorbed was not significantly different from the prepregnancy value. This increase persisted, however, and by 12 weeks postpartum, the amounts reabsorbed were significantly greater than those before conception. The general trend throughout pregnancy, therefore, was similar to that followed by maternal serum uric acid concentrations.