[Determination of blood cystatin C in pregnant women during labor and in their newborns].

INTRODUCTION: Human cystatin C is a basic low molecular mass protein (M(r) = 13,359) freely filtered by the glomerulus and almost completely reabsorbed and catabolized by the proximal tubular cells. In this study, we determined maternal and neonatal serum cystatin C levels both in a group of healthy pregnant women and in their newborns over the first five days of life. PATIENTS AND METHODS: Fifty healthy pregnant women, aged from 19 to 40 years, were selected. Newborns (31 males, 19 females) demonstrated the 1-min Apgar score ranging between 8 and 10, and the 5-min between 9 and 10. Their gestational age (GA) ranged between 37 and 43 weeks. Cystatin C was determined by using the cystatin C PET kit (Dako, Milano, Italy). We also determined serum creatinine and urea in all patients by using the Ektachem enzymatic assay (Ortho Diagnostic Division, Milano, Italy). RESULTS: In pregnant women, serum cystatin C was 1.52 +/- 0.39 mg/L, ranging from 0.69 to 2.30 mg/L. Serum creatinine was 58.9 +/- 11.5 mumol/L, and serum urea was 3.117 +/- 0.729 mmol/L. In newborns, serum cystatin C was at birth 2.29 +/- 0.52 mg/L, ranging from 1.17 to 4.84 mg/L. Subsequently, cystatin C significantly decreased over the first five days of life. Serum creatinine was at birth 80.08 +/- 14.26 mumol/L. By using analysis of variance (ANOVA) we found a statistically significant difference between maternal and neonatal cystatin C (p < 0.001) as well as between maternal and neonatal creatinine (p +/- 0.001). However, no correlation has been demonstrated by simple linear regression between maternal and neonatal cystatin C (r = 0.05), while maternal and neonatal creatinine significantly correlated (r = 0.45). CONCLUSIONS: Our preliminary findings suggest that cystatin C does not cross the placental barrier. Thus, in the neonate cystatin C serum levels may solely derived from himself.