A case control study conducted on 120 women coming to Cairo University Maternity Hospital .Patients who meet the inclusion criteria were asked to participate in the study and a verbal consent was obtained from each patient. Patients will be divided into three equal groups (A, B, C). A single dose of the drug (placebo or HBB 20mg or HBB 40 mg) will be injected intravenously slowly to groups A, B, C respectively. Labouring mothers will be monitored in bed. Vaginal examination will be conducted every two hours. The duration of the first stage was calculated from the time of cervical dilatation of three to four centimeters in active labour until a fully dilated cervix will be observed