Initiation of human parturition. III. Fetal membrane content of prostaglandin E2 and F2alpha precursor.

Unesterified arachidonic acid is the obligatory precursor of the prostaglandins (PG), PGF2alpha and PGE2. In order to ascertain whether or not the human fetal membranes could represent a storage site for prostaglandin(s) precursor, the fatty acid content of human fetal membranes was measured. Approximately 20% of the fatty acids found in fetal membranes obtained from near-term, non-laboring women was arachidonic acid, whereas only 0.4% of the fatty acids of the parietal peritoneum of the mother is arachidonic acid. A small but significant decrease in the arachidonic acid concentration was found in the fetal membranes obtained from laboring women compared to that found prior to labor. On the other hand, the concentration of palmitic acid was increased in membranes obtained during labor while no significant changes in concentration in the remaining fatty acids were observed in membranes from laboring compared to non-laboring near-term gravidas. The significance of these observations in relation to the availability of prostaglandin precursor and the initiation of human parturition is considered.