Topographic differences in amniotic fluid concentrations of prostanoids in women in spontaneous labor at term.

These studies were designated to determine if there are differences in prostanoid concentrations between amniotic fluid (AF) retrieved transvaginally from the membrane forebag (lower or forebag compartment) and fluid retrieved by transabdominal amniocentesis from the 'upper compartment' in women in labor. Fluid was retrieved from 53 women in active labor who underwent transabdominal and transvaginal amniocentesis. Fluid was assayed for prostaglandin E2 (PGE2) and prostaglandin F2 alpha (PGF2 alpha), 13,14-dihydro-15-keto-prostaglandin F2 alpha (PGFM), thromboxane B2 (TXB2), and 6-keto-prostaglandin F1 alpha (6-k-PGF1 alpha) using sensitive and specific radioimmunoassays. Concentrations of all prostanoids measured were significantly higher in fluid retrieved by transvaginal than transabdominal amniocentesis; the magnitude of the increase (measured as the ratio of concentrations in the lower/upper compartment) was higher for PGF2 alpha and TXB2 than for the other prostanoids measured; for each prostanoid measured, there was a significant correlation between the concentration in the upper and lower compartment.