AMNIOTIC-FLUID BIOCHEMISTRY IN 2ND-TRIMESTER TRISOMIC PREGNANCIES - RELATIONSHIPS TO FETAL ORGAN MATURATION AND DYSFUNCTION

Protein and enzyme patterns were investigated in amniotic fluid sample s of 12 trisomy 21 and five trisomy 18, between 11 and 16 weeks and of a control group of 50 chromosomally and anatomically normal pregnanci es at the same gestational age. Positive correlations were found betwe en gestational age and the concentration of urea (P<0.05), creatinine (P<0.01), beta 2-microglobulin (P < 0.0001), hCG (P < 0.01), ALP (P < 0.001), LAP (P < 0.0001) and GGT (P < 0.0005) in the amniotic fluid of euploid pregnancies. There were also significant correlations between the concentrations of the different variables measured except for hCG and AFP. Different protein and enzyme patterns were found in the amni otic fluid of aneuploid pregnancies where only beta 2-microglobulin co ncentration was significantly correlated with advancing gestational ag e. The beta 2-microglobulin concentration was significantly (P<0.05) h igher in aneuploid fetuses presenting with hydrops compared to those w ithout. These findings suggest that the changes in amniotic compositio n found during the fourth month of normal pregnancies reflect mainly t he maturation of the fetal renal glomerular function and the arrival o f enzymes from the digestive and respiratory tract into the amniotic c avity. In trisomy 21, there is evidence of a delay in the maturation o f these organs whereas in trisomy 18, there is a reduced production of most proteins and enzymes. (C) 1998 Elsevier Science Ireland Ltd. All rights reserved.