[...]... Total duration of labor (hours) Stage of labor Duration of the first stage (hours) Duration of the second stage (minutes) Duration of latent phase (hours) Rate of cervical dilatation during active phase (cm/h) Duration of the third stage (minutes) Multiparas Total duration of labor (hours) Stage of labor Duration of the first stage (hours) Duration of the second stage (minutes) Duration of latent phase... (ie, cervix, pelvic floor musculature), both of which offer varying degrees of resistance to fetal expulsion The bony pelvis is comprised of the greater and lesser pelvis and is divided by the pelvic brim Its anatomic boundaries are made up of the sacral promontory, the anterior ala of the sacrum, the arcuate line of the ilium, the pectineal line of the pubis, and the symphysis pubis The true pelvis can... Robinson J, Repke JT The initiation and management of labor In: Seifer DB, Samuels P, Kniss DA, editors The physiologic basis of gynecology and obstetrics Baltimore: Lippincott Williams & Wilkins; 2000 p 422; with permission.) 154 liao et al Passage The passage through which the fetus must pass during normal labor and delivery consists of the bony pelvis and the soft tissues of the birth canal (ie, cervix,... a physiologic and continuous process The factors responsible for the onset and maintenance of normal labor at term are poorly understood and continue to be under active investigation Although data exist to describe the average duration of labor, there is also a great deal of biologic variability An improved understanding of the causes and mechanisms of labor will improve the ability of clinicians to... hour and 2 hours, respectively [56] If there is continued progress and no evidence of maternal or fetal compromise, however, longer times are not associated with increased morbidity Third stage The third stage of labor refers to the time from delivery of the baby to separation and expulsion of the placenta and fetal membranes The three classic signs of placental separation are (1) lengthening of the... Characteristics of normal labour in different racial groups Br J Obstet Gynaecol 1975;82(8):593 – 601 [55] Studd J Partograms and nomograms of cervical dilatation in management of primigravid labour BMJ 1973;4(5890):451 – 5 [56] American College of Obstetricians and Gynecologists Dystocia and augmentation of labor Practice bulletin No 49 Washington, DC7 American College of Obstetricians and Gynecologists;... maternal bony pelvis and its musculature, and it is mediated by the basal tone of the fetal musculature  Expulsion Expulsion refers to delivery of the body of the fetus After delivery of the head and external rotation, further descent brings the anterior shoulder to the level of the symphysis pubis The anterior shoulder rotates under the symphysis pubis, after which the rest of the body usually delivers... to take place by 36 weeks is often an early sign of cephalopelvic disproportion [4]  Descent Descent refers to the downward passage of the presenting part through the pelvis Descent of the fetus is not a steady, continuous process The greatest rate of descent occurs during the deceleration phase of the first stage and during the second stage of labor  Flexion Flexion of the fetal head occurs passively... passively as the head descends because of the shape of the bony pelvis and the resistance of the soft tissues of the pelvic floor Although flexion of the fetal head onto the chest is present to some degree in most fetuses antepartum, complete flexion usually only occurs during the course of labor With the head completely flexed, the fetus presents the smallest diameter of its head (suboccipito-bregmatic... the handle while gently elevating the forcep blade with the index and middle fingers The handle of the anterior blade is then elevated to lock the handles The shanks should be angled toward the occiput Rotation with classical forceps uses a wide arcing motion, similar to turning a handle on a wrench (unlike the twisting motion used with the Kielland forceps, which is not unlike turning the handle of . distention (stretch) of the uterus, and through secretion of neurohypophyseal hormones and other stimulators of prostaglandin synthesis. Mechanics of normal labor Uterine. Repke JT. The initiation and management of labor. In: Seifer DB, Samuels P, Kniss DA, editors. The physiologic basis of gynecology and obstetrics. Baltimore: