BACKGROUND: A comprehensive knowledge of the nature and origin of amniotic fluid (AF) proteins should provide valuable information on developmental changes in fetal gene expression. In this study. AF proteins were analysed by two-dimensional electrophoresis (2-DE).

SUBJECTS: 18 healthy women (age, M±SD: 37.6±7.6 years) with normal singleton pregnancies.

METHODS: AF samples were obtained by mid-trimester amniocentesis(gestational age 16.6 ± 1.2 weeks, n=14) or during elective cesarean section near term (37.6 ± 3.7 weeks, n=4). 2D-E was performed using an immobiline-polyacrylamide system, and proteins were identified by matching with known biological fluid 2D-E databases, immunoblotting or N-terminal sequencing.

RESULTS: Protein species were 700-900/gel, with spots: A) matching proteins of 2-DE plasma database (n=34), B) matching cerebrospinal fluid proteins(n=10) and C) previously unreported Identified proteins included IGFBP-1, placental protein 14, β2-microglobulin, procollagen α-1(I) C-terminal propeptide, procollagen α-1(III), and a perlecan fragment Significant developmental changes in the expression of α-feto-protein, IGFBP-1, placental protein 14, and β2-microglobulin were observed. Mid-gestation AF showed α-feto-protein, but no haptoglobin (Hpt) α and β chains or hemopexin (Hpx), while Hpx and Hpt were evidenced near term.

CONCLUSION: AF protein maps may be first used as the reference database for the analysis of developmental defects of the human fetus. Mid-gestation AF protein patterns; 1) closely resemble those of fetal and preterm infant sera; 2) show significant non-material components; 3) considerably evolve during physiological pregnancies.