plasma concentrations of oxytocin in nine spontaneous labors ( group 1 ) , nine amniotomy-induced labors ( group 2 ) , six prostaglandin f2 alpha-induced labors ( group 3 ) , and five prostaglandin e2-induced labors ( group 4 ) were determined at the stages of 1 to 7 days preceding the onset of labor , onset of labor , and established labor , by means of unextracted radioimmunoassay .
C0474461
spontaneous labors
C0022864
labor