Preterm birth is one of the most important causes of perinatal morbidity and mortality worldwide. Prevention and treatment of preterm labor is important, not as an end in itself, but as a means of reducing adverse events for the neonate. A wide range of tocolytics, drugs used to suppress uterine contractions, have been tried. Magnesium sulfate (MgSO4) is the most widely used tocolytic at the American University of Beirut Medical Center despite the fact that an effective tocolytic role of MgSO4 has never been established. Moreover, the currently available data are suggestive of deleterious fetal effects of MgSO4 in the setting of preterm labor to the extent that some authorities are recommending abandoning it for routine use as a tocolytic therapy. Calcium channel blockers have the ability to inhibit contractility in smooth muscle cells. Consequently, nifedipine has emerged as an effective and rather safe alternative tocolytic agent for the management of preterm labor after several studies have shown that the use of nifedipine in comparison with other tocolytics is associated with a more frequent successful prolongation of pregnancy, resulting in significantly fewer admissions of newborns to the neonatal intensive care unit, and is associated with a lower incidence of respiratory distress syndrome. The unequivocal impact of this method of tocolysis on short term postponement of delivery and the opportunity that this provides for affecting in-utero transfer and steroid administration has prompted many investigators to recommend focusing future trials on testing different dose regimens of nifedipine. To the best of the investigators' knowledge, no study comparing two different dose regimens of nifedipine has been previously published in the literature. The objective of their study is to compare the effectiveness of a high versus a low dose regimen in a total of 200 patients admitted with the diagnosis of preterm labor between 24 and 34 weeks of gestation. In addition, the investigators' study will try to assess the safety profile of the 2 dose regimens on the mother and the neonate by assessing a selected number of outcome variables. The data generated will be used to change their protocol for managing patients presenting with threatened preterm delivery and will fill the existing gap regarding the most effective and safest dose regimen of nifedipine in such patients.