The present invention relates to novel pyrrolidine derivative of formula (I), its geometrical isomers, its optically active forms as enantiomers, diastereomers, mixtures of these and its racemate forms, as well as salts thereof, wherein R1 is selected from the group comprising or consisting of H and C1-C6-alkyl, for the prevention and/or treatment of preterm labor, premature birth or dysmenorrhea.