Safety and Efficacy Study of Vaginal Misoprostol for Cervical Ripening and Induction of Labor

Inclusion Criteria: * Singleton pregnancy. * Aged 20 years or older. * At term (37 to 42 weeks inclusive gestation). * Cephalic presentation (normal lie). * No rupture. * Bishop score ≤6. * With an indication for labour induction. * Written informed consent. Exclusion Criteria: * Any contraindication to vaginal delivery. * Previous of uterine scar(Cesarean section or other uterine surgeries). * Heavy or repeated vaginal bleeding in third trimester of pregnancy. * Have a history of glaucoma,asthma or epilepsy. * Contraindication to prostaglandin use. * Known severe allergy to prostaglandin. * Placenta previa * Premature rupture of membranes * Placental abruption * Fetal malpresentation(Breech or Transverse) * Obvious cephalopelvic disproportion * Amniotic Fluid Index more than 250mm or less than 50mm * Fetal growth restriction * Fetal malformation * Fetal distress * Preeclampsia or eclampsia * Fetal macrosomia of prenatal diagnosis(B-type ultrasonic inspection/Abdomen estimates) * Intrahepatic cholestasis syndrome(ICP) * Pregnancy with severe heart, lung, liver, kidney, endocrine disease and immune dysfunction * Pregnancy with acute systemic infection * Pregnancy with Severe anemia * Cervical carcinoma * Some genital tract infection disease, such as active herpes infection * Take part in other clinical trials within three months. * The person that investigator thought not be enrolled.