“…22 , 94 , 100 , 127 , 130 , 131 , 132 , 155 , 158 , 166 , 170 , 187 , 188 , 194 , 199 , 209 , 234 , 236 , 237 , 239 , 243 Some studies use separate definitions for nulliparous and multiparous women. 96 , 133 , 190 , 226 In more recent studies, the definition of the American College of Obstetricians and Gynecologists (ACOG) and Society for Maternal-Fetal Medicine (SMFM) is often used to determine the time when a cesarean section for prolonged labor should be performed: at least six centimeters with ruptured membranes, 4 hours no progress with adequate uterine activity or 6 hours oxytocin administration with inadequate uterine activity and no cervical change. This definition does not distinguish between nulliparous and multiparous women.…”