Changes in prostaglandin F and 13,14-dihydro-15-keto-prostaglandin F concentrations in amniotic fluid at the onset of and during labour.

Concentrations of prostaglandin F (PGF) and its major circulating metabolite 13,14-dihydro-15-keto-PGF (PGFM) have been measured in amniotic fluid during spontaneous labour at term. Levels of both PGF and PGFM were significantly higher during early spontaneous labour, at a cervical dilatation of less than 4 cm, than before the onset of labour. Patients who started labour spontaneously but later required oxytocin therapy for failure to progress in first stage had lower levels of PGF and PGFM than patients who progressed adequately without oxytocin therapy. During spontaneous labour, concentrations of both PGF and PGFM increased significantly with advancing cervical dilatation. These indicate that the accumulation of prostaglandins in amniotic fluid during labour is not due to decreased metabolism. They furthermore provide the strongest evidence available so far for an increase in intrauterine prostaglandin synthesis during human parturition.