The presence of Co-A independent transacylase activity in amnion cells and the preferential transfer of arachidonic acid to acceptor-ethanolamine plasmalogen provide a satisfactory explanation to the questions raised by the observation that arachidonate-enriched ethanolamine plasmalogen increases in amnion late in gestation without alteration in the total amount of ethanolamine glycerophospholipids. The proposed mechanism also serves as a link between the observed changes in glycerophospholipid composition and the generation of PAF. We have emphasized a role for PAF in fetal lung maturation, the initiation and maintenance of parturition, and in certain complications associated with a premature delivery. Although PAF is known to be the most potent lipid mediator yet described and its importance in reproductive biology is well documented, it is our view that these events cannot be attributed solely to PAF and in all likelihood a number of autacoids participate in these processes.