100 parturient women were investigated (40 patients with physiological labor, 20 patients with urgent caesarian section and 40 patients with the planned caesarian section). The levels of substance P, neurokinins A and B, corticotropin-realising hormone, rellaxin, cortisol, prostaglandin F2, interleukins 6 and 8 in plasma and amniotic fluid in the first period of labor and during caesarian section were measured. It was shown that the increase of corticotropin-realising hormone, rellaxin and cortisol concentration in blood plasma along with low level of prostaglandin F2 in amniotic fluid promotes disorders of labor activity. Thus, the character of labor activity depends on not only the absolute amounts of bioactive substances but also on their correlation in the maternal blood and amniotic fluid.