Pattern of changes in the levels of serum urea and creatinine in normal pregnancy and at different periods of gestation – its association with age, parity and hemoglobin Status

The levels of serum urea and creatinine were determined in 134 pregnant women and 44 non pregnant controls. There was a significant (p=0.0094) decrease in urea levels between the pregnant (15.4± 4.3 mg/dl) and the nonpregnant group (17.3±3.2mg/dl) and a highly significant (p<0.0001) decrease in creatinine levels between the pregnant (0.66±0.11mg/dl) and nonpregnant controls (0.76±0.09mg/dl). The pregnant women were categorized into 4 groups (0-12w), (13-24w), (25-36w)and (37-40w) as per their weeks of gestation and the levels of urea and creatinine in these groups were analyzed. There was no significant change in urea levels at 0-12 weeks as compared to the controls .At 13-24 weeks there was a significant increase(p<0.0001) followed by a significant decrease from 25-40 weeks(p<0.0001). The serum creatinine levels decreased significantly across different periods of gestation.(p<0.0001). There were 56 uniparous and 78 multiparous women. There was no significant decrease in urea and creatinine levels with increasing parity or age or with decreasing hemoglobin levels. The progressive decrease in creatinine levels across the different periods of gestation can be attributed to increased glomerular filtration rate (GFR) and reduced clearance. However the changes in urea cannot be explained by increased GFR alone. Other factors like higher salvage of urea or increased N2 accretion by the mother may contribute to these variations. This study has also enabled us to establish a reference range for urea and creatinine in pregnancy.