Background: Cystatin C is a biomarker of renal function and other diseases. Physiologic changes during pregnancy can alter
it level and lead to misinterpretation of result.
Objective: To determine reference values for serum cystatin C in the first trimester of pregnancy.
Material and Method: The Thai singleton uncomplicated pregnant women who attend antenatal clinic at Maha Chakri
Sirindhorn Medical Center during August 2013 to December 2014 were included. Gestational age of individual was calculated
by last menstrual period or ultrasound scan. Demographic data and obstetrics outcomes were recorded. Peripheral blood was taken on the first prenatal visit. Serum cystatin C was measured by particle-enhanced turbidimetric immunoassay (PETIA) with ARCHITECT c Systems® (ABBOTT, Germany).
Results: A total of 48 pregnant women were eligible for the study. The overall mean and standard deviation of serum cystatin C was 0.58+0.08 mg/L. There was no significant correlation between serum cystatin C and creatinine level (r = 0.22, p-value = 0.13).
Conclusion: The reference value of serum cystatin C was established for Thai pregnant women in the first trimester. Further studies of its correlation to specific obstetrics conditions should be considered.

Keywords: Serum cystatin C, Pregnancy, First trimester