Evaluation of the fetal kidney maturation by assessment of amniotic fluid alpha-1 microglobulin levels

Objective: To evaluate the fetal renal maturation by assessment of amniotic fluid microproteins and to show these proteins originate from fetal urine. Study design: Amniotic fluid proteins (total protein, albumin, high molecu lar weight protein-HMWP, low molecular weight protein-LMWP, alpha(1)-microg lobulin and beta(2)-microglobulin) were determined in 39 pregnant women at delivery and by amniocentesis in 30 pregnant women. These values were compa red with first urine values of neonates with the same gestational age. Resu lts: Albumin was the largest protein component in the amniotic fluid. LMWP showed an increase in the amniotic fluid until the end of the second trimes ter; and as pregnancy advanced a progressive decrease occurred in parallel to fetal renal maturation. After 26 weeks' gestation, a strong correlation was identified between LMWP levels and alpha(1)-microglobulin, and between LMWP and beta(2)-microglobulin. No significant difference was detected betw een LMWP levels in the first urine of the neonates and in amniotic fluids. Conclusion: Microproteins in the fetal urine are of fetal origin. Fetal ren al maturation can be evaluated by measuring microproteins in the amniotic f luid. Fetal renal maturation is best reflected by alpha(1)-microglobulin. ( C) 2000 Elsevier Science Ireland Ltd. All rights reserved.