Abstract Introduction In 2010, Indonesia was ranked fifth in the world for the number of premature birth. Prematurity is a multifactorial problem. Preterm Labor (PTL) can occur spontaneously without a clear cause. To prevent PTL, its associated risk factors must be recognized first. Objective To analyze risk factors associated with the incidence of PTLMethod this is a cross sectional study using secondary data obtained from medical records in Haji adam malik general hospital, pirngadi general hospital and satellite hospitals in medan between January 2014 - December 2016.  Data were analyzed using chi square method and logistic regression test. Result 148 cases for each group of preterm labor and term labor were obtained in this study. Using logistic regression test, 3 factors with strong association to the incidence of preterm labor were identified. Antenatal Care frequency (OR 2,326; CI 95%), leucorrhea (OR 6,291; 95%), and premature rupture of membrane (OR 9,755; CI 95%)Conclusion : Antenatal Care frequency, leucorrhea and history of premature rupture of membrane may increase the incidence of Preterm Labor (PTL). Keyword : preterm labor, risk factor, premature rupture of membrane.