Background: There are two methods of pharmacologic and non- pharmacologic for reducing pain of delivery. It is necessary to be known effect of these drugs on the mother and fetus during labor adverse. Therefore, the purpose of this study was determination of effect of Fentanyl intravenously on pain severity during the active phase of labor.

Inclusion Criteria:

• multiparas pregnant women (gravid 2-7),
• term singleton pregnancy,
• cephalic presentation,
• low risk pregnancy with no history of drug tolerance (addiction),
• medical and mental diseases.

Exclusion Criteria:

• Respiratory rate ≤ 8 or maternal bradycardia (pulse rate less than 60).