Trimester-Specific Reference Intervals of Serum Urea, Creatinine, and Uric Acid Among Healthy Pregnant Women in Zhengzhou, China

Objective: To verify the differences in serum levels of urea, creatinine, and uric acid (UA) between pregnant and nonpregnant women and establish specific reference intervals of serum urea, creatinine, and UA for pregnant women, and thus help for the detection of kidney disease in pregnancy. Methods: Based on the selection criteria, 1312 apparently healthy pregnant women and 1301 nonpregnant women were enrolled in this study. The levels of serum urea, creatinine, and UA were compared between the pregnant and nonpregnant women. The differences in the 3 indicators among different age groups and trimesters in pregnant women were studied. Finally, reference intervals were established by nonparametric methods according to the recommendation of Clinical and Laboratory Standards Institute guideline C28-A3. Results: Compared with nonpregnant women, pregnant women had a significantly lower level of serum urea, creatinine, and UA (all P<.01), and no significant age-related differences in the 3 indicators were observed among the pregnant women (P>.05). However, the levels of these indicators were significantly different among the 3 trimesters (all P<.01 or P=.01). Accordingly, trimester-specific reference intervals of serum urea (1.6-4.4 mmol/L; 1.6-4.2 mmol/L; 1.6-4.4 mmol/L), creatinine (36-68 mu mol/L; 34-66 mu mol/L; 36-68 mu mol/L), and UA (122-297 mu mol/L; 129-327 mu mol/L; 147-376 mu mol/L) for trimesters 1, 2, and 3, respectively, were established. Conclusion: These newly established reference intervals will be valuable for the detection and monitoring of kidney disease in pregnancy.