IJSR International Journal of Scientific Research 2277 - 8179 Indian Society for Health and Advanced Research ijsr-10-1-33265 Original Research Paper Risk factor for unsuccessful rate of preterm labor inhibition with tocolytic agent in pregnant women 240/7-336/7 weeks of gestation at Maharat Nakhon Ratchasima Hospital Seevilai Dr. January 2021 10 1 01 02