The invention discloses a pharmaceutical composition containing oxytocin and melatonin in amounts therapeutically effective for inducing labor in a pregnant human patient. Preferably, the oxytocin content is reduced to mitigate unwanted side effects and the melatonin content synergistically enhances the oxytocin's labor-inducing effectiveness. Also disclosed is a pharmaceutical composition for treatment of a pregnant human patient experiencing pre-term labor characterized by early expression of melatonin receptors in myometrial cells, the composition containing one or more agents which interfere with melatonin binding to said receptors. Additionally, the invention includes a method of treatment effective in inducing labor in a pregnant human patient, the method comprising coadministering melatonin and oxytocin to the patient and a method of treating pre-term labor in a pregnant human patient manifesting early expression of melatonin receptors in her myometrial tissues, the method comprising administering to the patient an agent effective in blocking melatonin binding to the receptors.