Biochemical analyses of mesenchymal fluid in early pregnancy

Our purpose was to compare the biochemical composition of the fluid contained in pathologic and physiologic cavities in early pregnancy.

The level of urea, creatinine, electrolytes, enzymes, total protein, and alpha-fetoprotein and the affinity of alpha-fetoprotein for concanavalin A Sepharose was measured in samples of vesicular fluid from complete (n=2) and partial (n=1) mole, nuchal fluid (n=4), and cystic hygroma fluid (n=4). For comparison samples of maternal serum (n=32), amniotic fluid (n=32), coelomic fluid (n=15), and fetal blood (n=13) were obtained from normal pregnancies at 10 to 16 weeks' gestation.

Urea concentration was lower, whereas sodium, potassium, and total protein concentrations were higher in vesicular fluid than in amniotic and coelomic fluid. Urea, creatinine, sodium, potassium, chloride, and beta2-microglobulin concentrations did not vary between nuchal or cystic hygroma fluid and amniotic fluid or fetal serum. The concentration of total protein in nuchal and hygroma fluid was significantly lower than in fetal serum and significantly higher than in amniotic fluid. The amniotic fluid contained extremely high tau-glutamyltransferase concentration compared with the other fluids and fetal serum. Alkaline phosphatase and amylase were not detectable in coelomic fluid, fetal serum, or nuchal and hygroma fluid. The nuchal and hygroma fluid composition was similar except for total protein and alpha-fetoprotein concentrations, which were significantly higher in nuchal than in hygroma fluid. The vesicular fluid from the partial mole, fetal serum, and nuchal and hygroma fluid contained extremely high alpha-fetoprotein concentrations, which were significantly higher that those found in amniotic fluid. In complete mole alpha-fetoprotein molecules were of the yolk sac type, whereas they were of the liver type in nuchal and hygroma fluid.

The composition of vesicular fluid in complete mole reflects a possible origin from the maternal plasma, yolk sac, and trophoblast, whereas the composition of nuchal and cystic hygroma fluid suggests a leakage from the fetal circulation.