Increase of prostaglandin E and F equivalents in amniotic fluid during late pregnancy and rapid PG F elevation after cervical dilatation.

Prostaglandin E and F equivalents in amniotic fluid from 163 women were determined after amniocentesis using chromatographic group separation and radioimmunoassay. Both PG E and F equivalents remained unchanged at levels below 100 pg/ml until week 34 of gestation and increased exponentially thereafter reaching levels of 745 and 821 pg/ml at weeks 41/42. Cervical dilatation at weeks 9 - 12 and 37 - 42 of pregnancy resulted in rapid elevations of PG F equivalents, but not of PG E, by factors of about 3 and 13, respectively. It is assumed that the slowly increasing production of both PG E and F demonstrated during the last weeks of pregnancy is connected with maturation processes within the feto-placental unit preceding birth, whereas the rapid formation of high PG levels channeled to the PG F pool in response to mechanical stimuli resembles the processes closely related to the trigger mechanisms for the onset and progress of spontaneous labour at term.