Background and Aim: In obstetrics, calcium antagonists, in particular nifedipine, have become increasingly popular for the management of preterm labor and are more effective tocolytic agents than beta 2-sympathomimetics. Our aim was to evaluate the effects of oral nifedipine therapy on ultrasonographic cord blood flow parameters in pregnant women with short cervical length. Materials and Methods: In a case-series study, 20 patients at risk of preterm labor with shortening cervix in serial examinations were included. Patients received oral nifedipine administered 40 mg per day until 37w of gestational age (GA). Umbilical artery Doppler parameters including systolic/diastolic ratio (SD) and pulsatility index (PI) were recorded before and biweekly after nifedipine prescription. Results: The mean of age was 25.55±4.58 years. The mean cervical length was 19.68±6.32. nifedipine consumption was initiated at the 26.4±4.12w and was terminated at 36.10±2.65w. The side effects of nifedipine were occurred in 2 patients (10%). In no patient no SD and PI measure get out of normal values. In contrast to PI, after nifedipine consumption SD was significantly higher than before (2.28±0.45 vs. 2.65±0.21). Two neonates (10%) were delivered before 37w and less than 2500gr. Just one neonate needed NICU stay. Conclusion: Oral nifedipine can be used as a safe and effective tocolytic treatment in patients at risk of preterm labor with shortened cervical length.