The objective is aimed to Assessing risk factors for unsuccessful rate of uterus contraction inhibition in pregnant women 240/7-336/7 weeks of gestation in Maharat Nakhon Ratchasima Hospital The retrospective cohort study approved by the Research Ethics committee of, Maharat Hospital, Nokhon Ratchasima Province Thailand studying pregnant women who were diagnosed with preterm labor pain with gestrational age of 240/7-336/7 weeks at the delivery ward of Maharat Nakhon Ratchasima Hospital and received Dexamethasone(corticosteroid) for the first time in every case between 1 January 2016 – 31 December 2018. From 361 pregnant women with preterm labor pain, 169 women were successful inhibition which was 54.29%. The group with failure inhibition were 165 women which was 45.71%. The factors relating to unsuccessful inhibition of uterus contraction were ANC less than 5 times, Adjusted odd ratios(AORs) 1.74; 95%CI 1.01-3.03, multiple pregnancy AORs 4.42 ; 95%CI 1.96-9.97 Cervical dilatation ≥3 cm AORs 5.93; 95%CI 3.44-10.22, the Effacement ≥ 80%, AORs 3.39; 95%CI 2.07-5.55, transfer from another hospital AORs 13.96; 95%CI 5.24-37.19. The research concludes that the factors relating to unsuccessful inhibition of uterus contraction were ANC less than 5 times, multiple pregnancy, Cervical dilatation ≥3 centimeters, Effacement ≥ 80%,and pregnant women referred from Secondary care center