The ability of a series of new 17 alpha-Hydroxyprogesteron derivatives (acetomepregnol, AMOL phenyl propyoate, butagest) in preventing the prostaglandin-induced preterm labor was experimentally studied in mice. It was found that all the synthetic gestagens studied, especially butagest, maintained pregnancy in all test animals on the model of enzaprost F induced abortion. The proposed progestogens can be used to prevent abortion in pregnancies in cases of risk from diseases connected with excess prostaglandin secretion.