Preterm labor is defined as delivery of a live birth after 20 weeks gestation and before completed 37 weeks’ gestation. The incidence of preterm birth ranges between 10% and 12.5% of all births .Aim of the work assessment of the efficacy and safety of oral Nifedipine compared with β-mimetics: Ritodrine, as a maintenance tocolytic therapy in preterm birth. The study found that Using Nifedipine as a maintenance tocolytic therapy in preterm birth is better than Ritodrine.