Background: Preterm birth is a significant cause of perinatal morbidity and mortality and that becomes a major challenge in perinatal health care. Various pharmacological agents that inhibit uterine contractions are used in clinical practice to prevent preterm delivery. The maternal and fetal side-effect profiles of tocolytic agents are becoming an important consideration in selecting the drug of choice. Nifedipine, a dihydropyridine calcium entry blocker, is an effective tocolytic agent with low toxicity and teratogenicity, while carrying potential maternal as well as fetal vascular side effects due to its action on vascular smooth muscle. This study was performed to asses nifedipine use as tocolytic agent in preventing preterm birth, and assesing maternal as well as fetal vascular side effects.Methods: This experimental study with one-group pretest-posttest design was performed in 30 pregnant women undergoing nifedipine as tocolytic. Doppler assessment of uterine, umbilical and fetal middle cerebral arteries, ductus venosus, and cerebroplacental ratio was performed before and 48 hours after nifedipine therapy. Wilcoxon's signed ranks test was used to analyze the difference between the two variables. A P-value of < 0.05 was considered significant.Results: The result of the study showed nifedipine was associated with a significant decreased of pulsatility index uterine artery (p = 0.016; p-value<0.05) and umbilical artery (p = 0.037; p-value<0.05) after 48 hours therapy, while pulsatility index of fetal middle cerebral arteries, ductus venosus, and cerebroplacental ratio did not change significantly.Conclusion: The study concluded that nifedipine as tocolytic increased blood flow of uterine artery and umbilical artery after 48 hours therapy.