Structural changes and variations of uric acid in normal pregnancy.

Fifteen normal pregnant women were studied. Serial measurements of serum total, free and bound uric acid and their clearances were done in early (10-20 weeks), mid- (20-30 weeks) and advanced (30-40 weeks) pregnancy, and after delivery (4-5 weeks). The following was observed. 1. A decrease in early and mid-pregnancy of total and free uric acid (p less than 0.001). 2. A gradual increase from the early to advanced pregnancy of bound uric acid (p less than 0.001). 3. An increase in early and mid-pregnancy of total uric acid clearance and a similar but more pronounced increase of free uric acid clearance (p less than 0.001). These findings explain many differences in previous conflicting reports concerning the metabolic behavior of uric acid, and place future investigation thereof on a more promising basis in normal and abnormal pregnancy.