Plasma levels of 13,14-dihydro-15-keto prostaglandin F2α, estrogens, and progesterone during stretch-induced labor at term

The uterus of six healthy multiparous women at term was mechanically stretched by a rubber catheter and balloon. Apparent labor was inaugurated in all cases within 5 hours and increased progressively with time. Advanced cervical softening and dilatation were also evident after the stretch treatment. Significant increases in the levels of 13,14-dihydro-15-keto-prostaglandin F_2α (PGFM) were observed with the progress of treatment (P < 0.01). Plasma estrogens and progesterone levels did not change significantly during the treatment (P > 0.05). Stretching and/or resulting uterine contractions appear to induce the secretion of prostaglandin F_2α (PGF) from the organ, which in turn seems to be involved in both cervical softening, and the onset and progress of labor, under stable conditions of plasma estrogens and progesterone.