Urea and Creatinine Clearances in the Three Trimesters of Pregnancy

Abstract

The aim of this study was to determine the creatinine and urea clearances, as indices of glomerular filtration rate (GFR) during the three trimesters of pregnancy. A total of 108 healthy subjects between the ages of 18 and 37years were divided into non-pregnant women (28+5years, n=30), 1st trimester of pregnancy (28+5years, n=18), 2nd trimester of pregnancy (28+4years, n=30). Serum and urine samples were collected at mid-trimester period. Creatinine and urea concentrations in serum and urine were determined using Jaffe’s method for creatinine and the urease (Ccr) and urea clearance (Uurea) in the three trimesters when compared with the non-pregnancy value. The increase in creatinine clearance peaked in the second trimester (64.76+1.37 (non-pregnancy vs. 2nd trimester), while the increases of 34.50+3.68ml/min (non-pregnancy vs. 1st trimester), and 38.63+1.56 (nonpregnancy vs. 3rd trimester) were similar. These increases in Ccr were associated with a significant fall (p<0.01) in serum creatinine concentration. Similarly, there was a significant increase in the urea clearances in the 1st , 2nd and 3rd trimester of pregnancy with a peak in the second trimester; and it remained elevated during pregnancy. In contrast to blood creatinine concentration, blood urea concentration increased significantly (p<0.01) in all trimesters of pregnancy. It is concluded that GFR increases in pregnancy until term, with a peak at the second trimester.