Second Stage of Labor This stage begins when cervical dilatation is complete and ends with fetal delivery. The median duration is about 50 minutes for nulliparas and about 20 minutes for multiparas, but it can be highly variable (Kilpatrick and Laros, 1989) Lippincott Williams & Wilkins
In a woman of higher parity with a previously dilated vagina and perineum, two or three expulsive efforts after full cervical dilatation may suffice to complete delivery. Conversely, in a woman with a contracted pelvis or a large fetus or with impaired expulsive efforts from conduction analgesia or sedation, the second stage may become abnormally long.
The second stage generally takes from 30 minutes to 3 hours in primigravid women and from 5 to 30 minutes in multigravid women.
CONT. -Three phases of 2 nd stage: 1. Latent phase 2. Decent phase 3. Transition phase These phases are characteterized by maternal verbal and nonverbal behaviors, uterine activity, urge to bear down, and fetal descent.
Phases 2 nd stage: 1.Latent phase -Is a period of rest and relative calm -Fetus continues to decent passively through the birth canal and rotate to anterior position as result UT contraction
CONT. - Woman is quiet and relax with her eyes closed between contractions. - The urge to bear down is not well established and my not be experienced at all or only during the peak of contraction
Phase 2 nd stage 2. Descent phase (active pushing) - Strong urges to bear down as ferguson reflex is activated when the presenting part presses on the stretch receptor of the pelvic floor, the fetal station 1+, position is anterior.
Phase 2 nd stage 3. Transition phase - The presenting part on the perineum - Bearing down is more effective for promoting birth - woman more verbal about pain, she may scream or swear and may act out of control
Duration of 2 nd The duration of 2 nd stage of labor is influenced by several factors : 1. Effectiveness of the primary and secondary powers of labor 2. Type and amount of analgesia used 3. Physical and emotional condition 4. Position, activity level, parity
Duration of second stage 5. Pelvic adequacy of the laboring woman (size, presentation, position of the fetus) 6. Nature of support the woman receives
CONT. If the woman has been given epidural analgesia pushing can last more than 2hrs, anaglesia reduce the urge bear down and limits the woman ’ s ability to attain an upright position to push
CONT. -Commonly 2 nd stage of more than 2hrs may be consider prolonged in woman without analgesia and is reported to the primary of health care provider using assessment to FTR and pattern, decent of the presenting part, quality of UT contraction and the status of the woman. - premature interventions with episiotomy or forceps or vacuum assisted birth can be avoided.
Mechanism of labor. Six movements of the baby enable it to adapt to the maternal pelvis: descent, flexion, internal rotation, extension, external rotation, and expulsion.
1- DESCENT. Descent is brought about by the force of the uterine contractions, maternal bearing-down (Valsalva) efforts, and, if the patient is upright, gravity. 2- FLEXION. Partial flexion exists before labor as a result of the natural muscle tone of the fetus. During descent, resistance from the cervix, walls of the pelvis, and pelvic floor cause further flexion of the cervical spine, with the baby's chin approaching its chest.
In the occipitoanterior position, the effect of flexion is to change the presenting diameter from the occipitofrontal to the smaller suboccipitobregmatic. In the occipitoposterior position, complete flexion may not occur, resulting in a larger presenting diameter, which may contribute to a longer labor.
3- INTERNAL ROTATION. In the occipitoanterior positions, the fetal head, which enters the pelvis in a transverse or oblique diameter, rotates so that the occiput turns anteriorly toward the symphysis pubis. Internal rotation probably occurs as the fetal head meets the muscular sling of the pelvic floor. It is often not accomplished until the presenting part has reached the level of the ischial spines (zero station) and therefore is engaged.
In the occipitoposterior positions, the fetal head may rotate posteriorly so the occiput turns toward the hollow of the sacrum. Alternatively, the fetal head may rotate more than 90 degrees, positioning the occiput under the pubic symphysis and thus converting to an occipitoanterior position
Crowning Occurs when the largest diameter of the fetal head is encircled by the vulvar ring. At this time, the vertex has reached station +5. When necessary, an incision in the perineum (episiotomy) may aid in reducing perineal resistance, although current management is to allow the fetus to deliver without an episiotomy.
4- Extension: The head is born by rapid extension as the occiput, sinciput, nose, mouth, and chin pass over the perineum. In the occipitoposterior position, the head is born by a combination of flexion and extension. At the time of crowning, the posterior bony pelvis and the muscular sling encourage further flexion. The forehead, sinciput, and occiput are born as the fetal chin approaches the chest. Subsequently, the occiput falls back as the head extends, and the nose, mouth, and chin are born.
5- EXTERNAL ROTATION. In both the occipitoanterior and occipitoposterior positions, the delivered head now returns to its original position at the time of engagement to align itself with the fetal back and shoulders. Further head rotation may occur as the shoulders undergo an internal rotation to align themselves anteroposteriorly within the pelvis.
6- EXPULSION. Following external rotation of the head, the anterior shoulder delivers under the symphysis pubis, followed by the posterior shoulder over the perineal body and the body of the child. Clinical management of the second stage. As in the first stage, certain steps should be taken in the clinical management of the second stage of labor.
Management of the Second Stage of Labor With full dilatation of the cervix, which signifies the onset of the second stage of labor, a woman typically begins to bear down, and with descent of the presenting part she develops the urge to defecate.
Uterine contractions and the accompanying expulsive forces may last 1 /2 minutes and recur at an interval no longer than 1 minute.
Maternal Expulsive Efforts In most cases, bearing down is reflexive and spontaneous during second-stage labor, but occasionally a woman may not employ her expulsive forces to good advantage and coaching is desirable. Her legs should be half-flexed so that she can push with them against the mattress. Instructions should be to take a deep breath as soon as the next uterine contraction begins, and with her breath held, to exert downward pressure exactly as though she were straining at stool.
She should not be encouraged to "push" beyond the time of completion of each uterine contraction. Instead, she and her fetus should be allowed to rest and recover. During this period of active bearing down, the fetal heart rate auscultated immediately after the contraction is likely to be slow, but should recover to normal range before the next expulsive effort. Gardosi and associates (1989) have recommended a squatting or semisquatting position using a specialized pillow.
They claim that this shortens second-stage labor by increasing expulsive forces and by increasing the diameter of the pelvic outlet. Eason and colleagues (2000) performed an extensive review of positions and their effect on the incidence of perineal trauma. They found that the supported upright position had no advantages over the recumbent one.
As the head descends through the pelvis, feces frequently are expelled by the woman. With further descent, the perineum begins to bulge and the overlying skin becomes stretched. Now the scalp of the fetus may be visible through the vulvar opening. At this time, the woman and her fetus are prepared for delivery.
Preparation for Delivery Delivery can be accomplished with the mother in a variety of positions. The most widely used and often the most satisfactory one is the dorsal lithotomy position. At Parkland Hospital the lithotomy position is not mandated for normal deliveries. In many birthing rooms delivery is accomplished with the woman lying flat on the bed.
For better exposure, leg holders or stirrups are used. In placing the legs in leg holders, care should be taken not to separate the legs too widely or place one leg higher than the other, as this will exert pulling forces on the perineum that might easily result in the extension of a spontaneous tear or an episiotomy into a fourth-degree laceration. The popliteal region should rest comfortably in the proximal portion and the heel in the distal portion of the leg holder.
The legs are not strapped into the stirrups, thereby allowing quick flexion of the thighs backward onto the abdomen should shoulder dystocia develop. The legs may cramp during the second stage, in part, because of pressure by the fetal head on nerves in the pelvis. Such cramps may be relieved by changing the position of the leg or by brief massage, but leg cramps should never be ignored.
Preparation for delivery should include vulvar and perineal cleansing. If desired, sterile drapes may be placed in such a way that only the immediate area about the vulva is exposed. In the past, the major reason for care in scrubbing, gowning, and gloving was to protect the laboring woman from the introduction of infectious agents.
Spontaneous Delivery Delivery of the Head With each contraction, the perineum bulges increasingly, and the vulvovaginal opening becomes more dilated by the fetal head, gradually forming an ovoid and finally an almost circular opening. This encirclement of the largest head diameter by the vulvar ring is known as crowning.
Unless an episiotomy has been made, the perineum thins and, especially in nulliparous women, may undergo spontaneous laceration. The anus becomes greatly stretched and protuberant, and the anterior wall of the rectum may be easily seen through it. Considerable controversy exists concerning whether an episiotomy should be cut.
Individualization and NO routine cut of an episiotomy is advocated. An episiotomy will increase the risk of a tear into the external anal sphincter or the rectum, or both. Conversely, anterior tears involving the urethra and labia are much more common in women in whom an episiotomy is not cut.
Ritgen Maneuver When the head distends the vulva and perineum enough to open the vaginal introitus to a diameter of 5 cm or more, a towel-draped, gloved hand may be used to exert forward pressure on the chin of the fetus through the perineum just in front of the coccyx. Concurrently, the other hand exerts pressure superiorly against the occiput.
it is customarily designated the Ritgen maneuver, or the modifiedRitgen maneuver. This maneuver allows controlled delivery of the head. It also favors extension, so that the head is delivered with its smallest diameters passing through the introitus and over the perineum. Mayerhofer and colleagues (2002) have challenged the use of the Ritgen maneuver on the grounds that this procedure was associated with more third- degree perineal lacerations and more frequent use of episiotomy.
They preferred the "hands-poised" method, in which the attendant did not touch the perineum during delivery of the head. This method had similar associated laceration rates and neonatal outcomes as the modified Ritgen maneuver, but with a lower incidence of third-degree tears.
Delivery of the Shoulders After its delivery, the fetal head falls posteriorly, bringing the face almost into contact with the maternal anus. The occiput promptly turns toward one of the maternal thighs and the head assumes a transverse position.
This movement of restitution (external rotation) indicates that the bisacromial diameter (transverse diameter of the thorax) has rotated into the anteroposterior diameter of the pelvis. Most often, the shoulders appear at the vulva just after external rotation and are born spontaneously. If delayed, immediate extraction may appear advisable.
The sides of the head are grasped with two hands, and gentle downward traction is applied until the anterior shoulder appears under the pubic arch. Some practitioners prefer to deliver the anterior shoulder prior to suctioning the nasopharynx or checking for a nuchal cord to avoid shoulder dystocia. Next, by an upward movement, the posterior shoulder is delivered.
The rest of the body almost always follows the shoulders without difficulty; but with prolonged delay, its birth may be hastened by moderate traction on the head and moderate pressure on the uterine fundus. Hooking the fingers in the axillae should be avoided because this may injure the nerves of the upper extremity, producing a transient or possibly a permanent paralysis.
Traction, furthermore, should be exerted only in the direction of the long axis of the neonate, for if applied obliquely it causes bending of the neck and excessive stretching of the brachial plexus. Immediately after delivery of the newborn, there is usually a gush of amnionic fluid, often tinged with blood but not grossly bloody.
Clearing the Nasopharynx To minimize aspiration of amnionic fluid, particulate matter, and blood once the thorax is delivered and the newborn can inspire, the face is quickly wiped and the nares and mouth are aspirated.
Nuchal Cord Following delivery of the anterior shoulder, a finger should be passed to the fetal neck to determine whether it is encircled by one or more coils of the umbilical cord. Nuchal cords are found in about 25 percent of deliveries and ordinarily do no harm. If a coil of umbilical cord is felt, it should be slipped over the head if loose enough. If applied too tightly, the loop should be cut between two clamps and the neonate promptly delivered
Clamping the Cord The umbilical cord is cut between two clamps placed 4 to 5 cm from the fetal abdomen, and later an umbilical cord clamp is applied 2 to 3 cm from the fetal abdomen. A plastic clamp (Double Grip Umbilical Clamp) that is safe, efficient, and fairly inexpensive is used.
Timing of Cord Clamping If after delivery, the newborn is placed at or below the level of the vaginal introitus for 3 minutes and the fetoplacental circulation is not immediately occluded by clamping the cord, an average of 80 mL of blood may be shifted from the placenta to the neonate. This provides about 50 mg of iron, which reduces the frequency of iron deficiency anemia later in infancy.
Some policies use to clamp the cord after first thoroughly clearing the airway, all of which usually requires about 30 seconds. The newborn is not elevated above the introitus at vaginal delivery or much above the maternal abdominal wall at the time of cesarean delivery.
Accelerated destruction of erythrocytes, as found with maternal alloimmunization, forms additional bilirubin from the added erythrocytes and contributes further to the danger of hyperbilirubinemia.
MIDWIFERY CARE DURING SECOND STAGE OF LABOR
Care and intervention in 2 nd -Latent phase * Encourages woman to listen to her body * Continues support measures allowing woman to rest * Suggest an upright position to encourage progression of decent
CONT. -Decent phase * Encourage respiratory of short breath holds and open glottis pushing. * Stresses normality and benefits of grunting sounds and expiratory vocalizations. * Encourage bearing down effort with urge to push.
CONT. * Encourage maternal movement and position changes upright, if decent is not occurring * Discourage long breath hold (no longer than 5 to 7sec) * Place the woman in lateral recumbent position to slow decent
CONT. - Transitional phase (8-10cm) * Encourage slow, gentle pushing * Explains that “ blowing away the contraction ” facilitates a slower birth of the head *
CONT. * Coaches woman to relax mouth, throat and neck to promote relaxation of pelvic floor * Apply warm compress to perineum to promote relaxation
Preparing For Birth 1.Maternal position 2.Bearing-down efforts 3.Fetal heart rate and pattern 4.Support of the father or partner 5.Supplies, instruments, and equipment
Maternal Position -The woman my want to assume various position for childbirth, and she should be encourage and assisted in attaining and maintaining her position of choice -Hason(1998) found that sitting and side Lying are the most common position assumed by women for their bearing down effort and birth
Upright position: - Facilitate birth and fetal decent - Reduce the duration of the 2 nd stage of labor - Reduce the need for episiotomy, forceps, or vacuum extractor
Mechanism Of Upright position 1. Straighten the longitudinal axis of the birth canal 2. Use gravity to direct the fetal head toward the pelvic inlet 3. Enlarge pelvic dimensions and restrict the encroach of the sacrum and coccyx into the pelvic outlet 4. Increase uteroplacental circulation 5. Enhance the woman ’ s ability to bearing down effectively
Upright position - Provides potential psychologic advantage it allows the mother to see the birth as occur, and maintain eye contact with attendant. -Upright position slightly increase the risk for 2 nd degree laceration and blood loss greater than 500ml (Donsante & shorten,2002)
Evidence -Use of supine position is associated with negative maternal, fetal and neonatal hemodynamic out comes. -Upright positions were associated with a slight reduction in second stage duration, reduction in assisted deliveries, reduction in epsiotomies increase in second degree tear, and fewer abnormal fetal heart rate. Robert J. Best practices in second stage of labor care.2007
Squatting position -Is highly effective to facilitating the decent and birth of the fetus, and is one of the best positions for the 2 nd stage of labor. - Firm surface is required. - Woman need side support.
Standing position -Uses the standing position for bearing down, her weight is born on both femoral heads, allowing the pressure in the acetabulum to cause the transverse diameter of the pelvic outlet to increase by up to 1cm (if the occiput has not rotated from the lateral to the anterior position.
Birthing chair -Used to provide women with a good physiologic position to enhance her bearing down effort during childbirth, although some women feel restricted by a chair - Most birthing chair are designed if emergency occurs, the chair can be adjusted to horizontal or trendelenburg position
Japanese Birth Chair
Side-Lying position -With the upper part of the woman ’ s leg held by the midwife or placed on a pillow low, is an effective for the 2 nd stage of labor
Semi-sitting position -Use to maintain good uteroplacental circulation and to enhance the woman ’ s bearing down effort -The episiotomy rate for nulliparas highest in this position - (Shorten, Donsante, &shorten,2002)
Hands – and knees position - Is an effective position for birth because it enhances placental perfusion. - Help rotate the fetus from posterior to an anterior position. -Facilitate the birth of the shoulders if the fetus is large. - Reduce perineal trauma.
Birthing Bed -The Birthing bed used according to the woman ’ s needs. - At the same time is excellent exposure for examinations, electrode placement and birth. - The bed can be positioned for administration of anesthesia. - The bed can be used to transport the woman to the operating room if C/S necessary.
Bearing down efforts -Is an involuntary response to the Ferguson reflex the midwife should encourage women to push as they feel like pushing (spontaneous pushing). -The midwife should monitor the woman ’ s breathing, so that the woman does not hold her breath for more than 5 to 7 seconds at time and should remind her to ventilate her lung fully by taking deep breaths before and after each contraction, this help maintain adequate O2 For the mother and fetus.
Fetal Heart Rate and Pattern - FHR must be checked if there is loss of variability, or if deceleration pattern developed. -The woman can be turned on her side. - O2 can be administer by mask at 8 to 10 L/m to mother. -If FHR does not become reassuring immediately the primary health care provider should be notified.
Support of the Father - During 2 nd stage, woman needs continuous support and coaching. -The support person who attends the birth in a delivery room is instructed to put on a cover gown, mask, hat, and shoes cover as agency policy.
CONT. - Partners are encourage to be present at the birth of their babies as cultural and personal expectation and beliefs. - In this way the psychologic closeness of the family unit is maintained, and the partner can continue to provide the supportive care given during labor.
CONT. -The woman and her partner need to have an equal opportunity to initiate attachment process with the baby.
Supplies, Instruments, and Equipment -The birthing table should be prepared during the transition phase for nulliparous, and during the active phase for multiparous woman. - Standard procedures for gloves,sterile packages, unwrapped sterile instruments and handling them to the primary health care provider.
CONT. -Radiant warmer and equipment are readied for the support and stabilization of the baby.
Birthing Room -Prepare the woman for delivery -The circulating nurse continues to support the woman. - The nurse auscultates FHR or evaluates the monitor every 5 to 15 minutes. - Oxytocin may be prepared to be administered after delivery of the placenta.
CONT. - midwife attending the birth my need to wear cap, protective eyewear, masks gown and gloves. - The woman draped with sterile drapes - midwife contact with the parents is maintained by touching, verbal comforting, explaining the reasons for care and sharing in the parents ’ joy at birth of their baby.
Immediate Assessment and Care of the Newborn - The care given after the birth focuses on assessing and stabilizing the newborn. - The midwife must watch the infant for any signs of distress and initiate appropriate interventions.
CONT. - A brief assessment of the newborn can be performed includes checking the airway and Apgar Score.
Perineal Trauma R/t child birth - Lacerations: -Most acute injuries or laceration of the perineum, vagina, uterus and their supportive tissues occur during child birth. - Laceration if not repair lead to genitourinary and sexual problem (pelvic relaxation, uterine prolapse, cystocele, rectocele, dyspareunia, urinary and anaL bowel dysfunction).
CONT. -Immediate repair: * Promotes healing * Limits residual damage * Decreases the possibility of infection
CONT. - Primary health care provider continue to inspect the perineum carefully and evaluate lochia to identify any missed damage during the early postpartum period.
Perineal Lacerations Degree of laceration: 1. First degree: laceration extends through the skin and structures superficial to muscle. 2. Second degree: Laceration extends through muscles of the perineal body
CONT. 3. Third degree: Laceration continues through the anal sphincter muscle. 4. Fourth degree: Laceration involves the anterior rectal wall.
CONT. - Special attention must be paid to third and fourth stage laceration so that woman retains fecal continence. - Measures are taken to promote soft stools (e.g. roughage, fluid, activity, and stool softeners) to increase comfort and healing.
CONT. - Antimicrobial therapy may be used - Enemas and suppositories are contraindication
Vaginal & Urethral laceration - Vaginal laceration occur in conjunction with perineal laceration - Vaginal laceration tend to extend up the lateral walls and if deep enough involve the levator ani muscle.
CONT. - Vaginal vault laceration may be circular and result from forceps rotation especially in the cephalopelvic disproportion, rapid fetal decent.
Cervical Injuries - Occur when the cervix retracts over the advancing fetal head. - This laceration occur at the angles of the external os, most are shallow, bleeding is minimal.
CONT. - Cervical injuries when extend to vaginal vault or beyond it into the lower uterine segment serious bleeding may occur. - Cervix laceration can have adverse effect on future pregnancies and child birth.
Evidence -The highest rate of trauma have consistently been observed in first births or operative vaginal deliveries (forceps or vacuum extraction). -Rate of trauma appear to increase with infant birth weight, maternal weight gain in pregnancy, and fetal malposition. - Use of episiotomy increases serious trauma to genital tract, especially third and fourth degree laceration. Leah L.Reduction Genital Tract Trauma at Birth
Episiotomy - Is an incision in the perineum to enlarge the vaginal outlet.
Episiotomy - Indication: 1. Facilitates vacuum or forceps assisted birth 2. Fetal distress 3. Facilitates the birth of large baby 4. Premature baby
Type of episiotomy 1. Median: -Is most commonly used - It is effective -Easily repaired -Least painful - Midline episiotomy are associated with a higher incidence of third and fourth degree of laceration.
Type of episiotomy 2. Mediolateral: Is used in operative births when need for posterior extension. - Fourth degree laceration may be prevented, third degree may occur. - Blood loss is greater, painful, difficult repair than midline.
Risk Factor associated with perineal trauma 1.Nulliparity 2. Maternal position 3. Pelvic inadequacy 3. Fetal malpresentation and position 4. Large baby 5. Use of instruments to facilitate birth
CONT. 6. Prolong second stage of labor 7. Fetal distress 8. Rapid labor
Evidence - Episiotomy should not be used unless indicated. Measures should be taken to avoid perineal trauma during labor to establish bonding early between mother and infant & to minimize perineal discomfort after birth. Karacam Z. Effects of episiotomy on bonding and mothers health. 2003
Perineal management - Warm compress - Massage - Kegel ’ s exercises in the prenatal and postpartum periods - Good nutrition, hygienic measures - As advocates, encourage women to use alternative birthing positions and use spontaneous bearing down effort.
Third stage of labor It is start from birth of the baby until the placenta is expelled.
Cont. -After the birth of the fetus, strong uterine contraction cause the placental site to shrink. This causes the anchor villi to break and the placenta to separate from its attachment, normally strong contraction that occur 5 to 7 minutes after the baby ’ s birth cause the placenta to be separated away from the basal plate. -- Placenta can ’ t detach it self from a flaccid uterus because the placental site is not reduced. -
Placenta Separation Is indicated by the following signs: 1.A firmly contracted fundus 2.A change in the uterus from a discoid to a globular ovoid shape 3.Sudden gush of dark blood 4.apparent lengthening of the umbilical cord 5.Vaginal fullness
Active approach may be used to manage of 3 rd 1- Expectant management involves natural, spontaneous separation and expulsion of the placenta by effort of the mother with clamping and cutting of the cord after pulsation ceases
CONT. 2. Use of the gravity or nipple stimulation to facilitate separation and expulsion. 3. A quiet, relaxed environment 4. Close skin to skin contact between mother and baby 5.Adminstration oxytocic medication after birth of the anterior shoulder.
Collaborative care 1. Placenta Examination and Disposal 2. Maternal physical status 3. Sign of potential problems 4. Care after placenta delivery 5. Care of the family during 3 rd stage 6. Family – Newborn relationship
Nursing diagnosis during 3 rd stage - Risk for infection - Anxiety - Compromised family coping
Care after the placenta delivery - Vulvar area cleansed with warm water or normal saline. - Perineal pad or ice pack is applied to perineum. - Birthing bed is repositioned. - Draped are removed - Dry linen is placed under the woman ’ s buttocks.
CONT. - Woman is provided with a clean gown and blanket which is warmed. - Transferred from birthing area to recovery area. - Side rails are raised during transfer. - Woman may be given the baby to hold during transfer or father may carry the baby or transport him in a crib.
CONT. - Maternal and neonatal assessments for the fourth stage of labor are instituted. - When fourth stage recovery is complete the woman may be transferred by wheelchair to a room on the postpartum unit
Care of the family during 3 rd stage - Most parents hold and examine the baby immediately after birth. - Skin to skin contact helps the mother maintain the baby ’ s body heat. - Care must be taken to keep the head warm. - Begin breastfeeding.
Positioning During the second stage of labor the upright position is the preferred position with the head of the bed at 45 degrees (eg, squatting, standing, upright kneeling, side-lying, knee- chest, and forward lean accompanied by a pelvic tilt). If the woman cannot tolerate or maintain an upright position, a lateral position can be used.
Benefits of the upright position include Increased pelvic diameter by as much as 30%. Decreased duration of the second stage of labor. Reduced intensity of pain and discomfort during the second stage of labor. Decreased perineal trauma (if pelvis and perineum given adequate support).
Pushing Techniques Pushing techniques can be either (1) delayed or (2) nondirected.
Delayed pushing waiting for fetal descent or initiation of Ferguson's reflex before pushing begins (ie, not pushing until the urge is felt even with complete cervical dilatation). The Ferguson's reflex is a physiologic response that is activated when the presenting part of the fetus is at least at a +1 station and is usually accompanied by spontaneous bearing-down efforts.
– Delayed pushing can be used with epidural anesthesia/analgesia as women cannot feel the urge to push. – Clinical practice recommends assessing women's knowledge of pushing techniques to include presence of Ferguson's reflex. – Also referred to as laboring down
Nondirected pushing â€” use of nontraditional pushing techniques such as open glottis or â€œtug-of-warâ€ techniques. Open glottis pushing for 4 to 6 seconds followed by slight exhaling (essentially pushing while exhaling/grunting) and repeating this pattern for 5 or 6 pushes/uterine contraction. There is minimal change in maternal blood pressure, thus minimal, if any, change in the FHR pattern. This method also relaxes the perineum, allowing the gentle delivery of the fetal head. Closed glottis pushing (holding breath for the count of 10) is not recommended. Tug-of-war â€” uses the natural bearing down effort of the abdominal muscles. A gown or short sheet can be tied in a knot at both ends. When the mother has the urge to push, she grabs one end of the gown or sheet and pulls as much as she can while the coach or nurse provides resistance by holding the other end. (Alternative way is to tie knot in one end and tie other end to squat bar of labor bed.) This method also causes minimal change in the maternal blood pressure, relaxes the perineum, and has been found to decrease the second stage of labor as much as 20 minutes. Use of birthing aids such as birthing balls, squat bars, birthing stools, and cushions to support the woman and her fetus.
Nursing Diagnoses Fear or Anxiety related to impending delivery Acute Pain related to descent of the fetus Risk for Infection related to episiotomy and tissue trauma
Nursing Interventions Minimizing Fear and Anxiety Monitor maternal vital signs as follows: – Blood pressure â€” every 5 to 15 minutes depending on the woman's status. – Pulse and respirations â€” every 15 to 30 minutes. – Temperature â€” every 1 hour when membranes have ruptured. Monitor FHR and uterine contractions every 15 minutes in low-risk women and every 5 minutes in high-risk women. P.1226 – Early decelerations and some fetal bradycardia may occur due to head compression. – There is normally no loss of variability during pushing. – Contractions may become less frequent, but intensity does not decrease. Explain procedures and equipment during pushing and delivery. Keep the woman or couple informed of their status. Provide frequent, positive encouragement. – Use of a mirror usually allows the woman to see her progress. Assist with positioning and pushing as outlined above.
Promoting Comfort Assist the woman to a comfortable position. – Left or right lateral, squatting, hand and knees, or semisitting positions may be used. – Assist the woman with pulling her legs back so her knees are flexed. – Teach the woman to put her chin to her chest so her body forms a â€œCâ€ shape while pushing. Evaluate bladder fullness, and encourage voiding or catheterize as needed. Evaluate effectiveness of anesthesia as indicated.
Preventing Infection and Promoting Safety Prepare the birthing room or delivery room using aseptic technique, allowing ample time for setup before delivery. Prepare the infant resuscitation area for delivery. Prepare necessary items for neonatal care. Notify necessary personnel to prepare for delivery. If delivery room is to be used, transfer the primigravida to the delivery room when the fetal head is crowning. The multigravida is taken earlier depending on fetal size and speed of fetal descent. Place all side rails up before moving. Instruct the woman to keep her hands off the rails, and move from the bed to the delivery table between contractions. If delivering in LDR (Labor, Delivery, Recovery) or LDRP (Labor, Delivery, Recovery, Postpartum) room, prepare labor bed for delivery in accordance with manufacturer's instructions. Prepare infant warmer and remainder of room for delivery. Position the woman for delivery using a large cushion for her head, back, and shoulders. Elevate the head of the bed. Stirrups or footrests may be used for foot support. Pad the stirrups. Place both legs in the stirrups at the same time to avoid ligament strain, backache, or injury.
Clean the vulva and perineal areas when the woman is positioned for delivery. Cleanse from the lower abdomen to the mons. Then clean the groin to the inner thigh on each side. Then clean each labia. Finally, clean the introitus. Guide the woman step by step during the delivery process. When the fetal head is encircled by the vulvovaginal ring, an episiotomy may be performed to prevent tearing. When the head is delivered, mother is instructed to stop pushing. Mucus is wiped from the infant's face, and the mouth and nose are aspirated with a bulb syringe. If thick or particulate meconium amniotic fluid is present, the mouth and nose are suctioned on the perineum with deep suction before the delivery of the body. If loops of umbilical cord are found around the neonate's neck, they are loosened and slipped from around the neck. If the cord cannot be slipped over the head, it is clamped with two clamps and cut between the two clamps. After this step, the woman is instructed to give a gentle push so the neonate's body may be quickly delivered. After delivery of the neonate's body and cutting of the cord, the neonate is shown to the parents and then placed on the maternal abdomen or taken to the radiant warmer for inspection and identification procedures. Practice standard precautions during labor and delivery.
Evaluation: Expected Outcomes Verbalizes positive statements about delivery outcome Reports decreased pain from proper positioning No infection results
Management of the Third Stage of Labor Immediately after delivery of the newborn, the size of the uterine fundus and its consistency are examined. If the uterus remains firm and there is no unusual bleeding, watchful waiting until the placenta separates is the usual practice. Massage is not employed, but the fundus is frequently palpated to make certain that the organ does not become atonic and filled with blood from placental separation. Signs of Placental Separation Because attempts to express the placenta prior to its separation are futile and possibly dangerous, the clinician should be alert to the following signs of placental separation: The uterus becomes globular and, as a rule, firmer. This sign is the earliest to appear. There is often a sudden gush of blood. The uterus rises in the abdomen because the placenta, having separated, passes down into the lower uterine segment and vagina, where its bulk pushes the uterus upward. The umbilical cord protrudes farther out of the vagina, indicating that the placenta has descended.
These signs sometimes appear within about 1 minute after delivery of the newborn and usually within 5 minutes. When the placenta has separated, it should be determined that the uterus is firmly contracted. The mother may be asked to bear down, and the intra-abdominal pressure may be adequate to expel the placenta. If these efforts fail, or if spontaneous expulsion is not possible because of anesthesia, then after ensuring that the uterus is contracted firmly, pressure is exerted with the hand on the fundus to propel the detached placenta into the vagina, as depicted and described in Figure 17–31. This approach has been termed physiological management, as later contrasted with active management of the third stage (Thilaganathan and colleagues, 1993).
Delivery of the Placenta Expression should never be forced before placental separation lest the uterus be turned inside out. Traction on the umbilical cord must not be used to pull the placenta out of the uterus. Inversion of the uterus is one of the grave complications associated with delivery (see Chap. 35, Inversion of the Uterus). As downward pressure toward the vagina is applied to the body of the uterus, the umbilical cord is kept slightly taut (see Fig. 17–31). The uterus is then lifted cephalad with the abdominal hand. This maneuver is repeated until the placenta reaches the introitus (Prendiville and associates, 1988b). As the placenta passes through the introitus, pressure on the uterus is stopped. The placenta is then gently lifted away from the introitus (Fig. 17–32). Care is taken to prevent the membranes from being torn off and left behind. If the membranes start to tear, they are grasped with a clamp and removed by gentle teasing (Fig. 17–33). The maternal surface of the placenta should be examined carefully to ensure that no placental fragments are left in the uterus.
Manual Removal of Placenta Occasionally, the placenta will not separate promptly. This is especially common in cases of preterm delivery (Dombrowski and colleagues, 1995). If there is brisk bleeding and the placenta cannot be delivered by the above technique, manual removal of the placenta is indicated, using the safeguards described in Chapter 35. It is unclear as to the length of time that should elapse in the absence of bleeding before the placenta is manually removed. Manual removal of the placenta is practiced sooner and more often than in the past. Some obstetricians practice routine manual removal of any placenta that has not separated spontaneously by the time they have completed delivery of the newborn and care of the cord in women with conduction analgesia. Proof of the benefits of this practice, however, has not been established, and most obstetricians await spontaneous placental separation unless bleeding is excessive. The American College of Obstetricians and Gynecologists (2003b) has concluded that there are no data to either support or refute the use of prophylactic antimicrobials when manual removal of the placenta is performed.
Active Management of the Third Stage Thilaganathan and associates (1993) compared a regimen of active management with syntometrine (5 units of oxytocin with 0.5 mg of ergometrine) and controlled cord traction with one of physiological management wherein the cord was not clamped and the placenta was delivered by maternal efforts. Among 103 low-risk term deliveries, active management resulted in a reduction in the length of the third stage of labor, but no reduction in blood loss compared with that of physiological management. Mitchell and Elbourne (1993) found that syntometrine administered intramuscularly concurrent with delivery of the anterior shoulder was more effective than oxytocin (5 units intramuscularly) alone in the prevention of postpartum hemorrhage. Duration of the third stage of labor and need for manual removal of the placenta were similar. Side effects of nausea, vomiting, and blood pressure elevations with ergometrine prevented any recommendation for its routine usage.
Fetal Heart Rate Patterns during Second-Stage Labor Decelerations are virtually ubiquitous. Melchior and Bernard (1985) reported that only 1.4 percent of more than 7000 deliveries did not have fetal heart rate decelerations during second-stage labor. Both cord compression and fetal head compression have been implicated as causes of decelerations and baseline bradycardia during second-stage labor. The high incidence of such patterns minimized their potential significance during the early development and interpretation of electronic monitoring. For example, Boehm (1975) described profound, prolonged fetal heart rate deceleration in the 10 minutes preceding vaginal delivery of 18 healthy infants. Subsequently, Herbert and Boehm (1981) reported another 18 pregnancies with similar prolonged decelerations during second-stage labor, but now associated with one stillbirth and one neonatal death. These experiences attest to the unpredictability of the fetal heart rate during second-stage labor. Spong and colleagues (1998) analyzed the characteristics of second-stage variable fetal heart rate decelerations in 250 deliveries and found that as the total number of decelerations to less than 70 beats/min increased, the 5-minute Apgar score decreased. Put another way, the longer a fetus was exposed to variable decelerations, the lower the Apgar score at 5 minutes. Picquard and co-workers (1988) analyzed heart rate patterns during second-stage labor in 234 women in an attempt to identify specific patterns to diagnose fetal compromise. Loss of beat-to-beat variability and baseline fetal heart rate less than 90 beats/min were predictive of fetal acidemia. Krebs and co-workers (1981) also found that persistent or progressive baseline bradycardia and baseline tachycardia were associated with low Apgar scores. Gull and colleagues (1996) observed that abrupt fetal heart rate deceleration to less than 100 beats/min, and associated with loss of beat-to-beat variability for 4 minutes or longer, was predictive of fetal acidemia. Thus, abnormal baseline heart rate—either bradycardia or tachycardia, absent beat-to-beat variability, or both—in the presence of second-stage decelerations is associated with increased but not inevitable fetal compromise (Fig. 18–25).
THE NORMAL THIRD STAGE OF LABOR Recognizing the sequence of events in the third stage of labor and understanding the mechanism of placental separation may aid the detection of cases at risk of third-stage complications and the management of pathology. Prostaglandin F (PGF), PGF2α, and oxytocin are the biochemical agents primarily involved in the third stage of labor. During the first and second stages of labor only PGF2α and oxytocin are significantly raised in maternal plasma compared to prelabor concentrations. At 5 minutes after birth, maternal PGF and PGF2α concentrations peak at about twice the levels found at the commencement of the second stage. A rapid increase in prostaglandin concentrations is also found in umbilical cord venous blood, suggesting that this postpartum prostaglandin surge originates in the placenta. After placental separation the concentrations decrease but at rates slower than the metabolic clearance of prostaglandin, indicating that its production continues in the deciduas and myometrium. Plasma oxytocin also drops to prelabor levels within 30 minutes of delivery, unless sustained by exogenous infusion.3 Continuous real-time ultrasound, performed during the third stage of labor, has revealed that the process of placental separation can be divided into four phases: 1. Latent—uterine wall at the placental site remains thin; placenta-free wall contracts 2. Contraction—thickening of uterine wall at the placental site 3. Detachment—actual separation of the placenta from the adjacent uterine wall 4. Expulsion—sliding of the placenta out of the uterine cavity.4
Forceful uterine contractions in the latent phase induce shearing forces between the uterine wall and the unyielding placental tissue, initiating the separation of the placenta. A wave of separation begins at one of the placental poles, usually at a point near to the lower segment, and propagates toward the fundus during the contraction and detachment phases. Separation of the fundal placenta begins at more than one of the placental poles, and the central part is last to separate. (This is the reverse of the Schultze and Mathews Duncan mechanisms described in most texts.) In almost half of the cases with a previous cesarean section the separation pattern was reversed, commencing at the fundus, suggesting that myometrial strength in the region of the uterine scar may have been compromised.5 Although spontaneous delivery of the placenta usually occurs within 10 minutes of the baby's birth, the third stage is not considered prolonged unless it lasts more than 30 minutes. Combs and Laros, in an 11-year study of 12,979 consecutive, singleton vaginal deliveries, demonstrated that the duration of the third stage followed a lognormal distribution, with a median of 6 minutes (interquartile range, 4 to 10 minutes). The prevalence of a third stage in excess of 30 minutes was 3.3%. Although stating that prophylactic oxytocic agents were not used routinely, their figures for duration are remarkably similar to those from the much larger series (45,869 singleton vaginal deliveries) reported by Dombrowski and colleagues, who estimated that using active management of the third stage, 90% of term placentas will deliver spontaneously by 15 minutes and only 2.2% will be undelivered at 30 minutes. A series of reports from our unit have also confirmed similar third-stage duration, and rates of prolonged third stage associated with different uterotonic agents (oxytocin [Pitocin, Syntocinon]: 1.4% to 1.8%; oxytocin/ergometrine [Syntometrine]: 1.6% to 2.8%; misoprostol [Cytotec]: 1.4%). Management Options There are markedly polarized views between those who believe in active management and those who believe in expectant (natural) management of the third stage. Active management of the third stage includes:
Administration of a prophylactic oxytocic agent or prostaglandin within 2 minutes of the baby's birth to induce uterine contraction Immediate cutting and clamping of the cord to enhance placental separation Placental delivery by controlled cord traction. In expectant management there is: No prophylactic oxytocic No cord clamping until pulsations cease Delivery of placenta is by maternal effort and gravity rather than cord traction.
Use of Prophylactic Uterotonic Agents There no longer appears to be any valid argument in favor of the physiologic approach, because two substantive studies comparing active management with expectant management have clearly indicated the advantages of active management. The Bristol trial, where active management had been the norm, and the Hinchingbrooke trial, where expectant management had been the norm, both demonstrated significant reductions in the incidence of PPH with active management compared with expectant management (5.9% versus 17.9% and 6.8% versus 16.5%, respectively). Both studies were terminated after interim analysis because the difference in PPH rate was so great.1112
Which Uterotonic Agent? In recent years, considerable attention has been paid to the choice of a uterotonic agent, in particular comparing the cheap and orally administered prostaglandin misoprostol with the combination agent Syntometrine (oxytocin/ergonovine). The findings seem to indicate that rectal misoprostol is a viable alternative to oxytocin in areas where storage and parenteral administration of drugs are problems (oxytocin has to be stored at 4°C to retain its efficacy, whereas tablets of misoprostol kept dry retain their efficacy even at tropical temperatures for several years or more), but its side effects (shivering, nausea, and diarrhea) and slightly lower efficacy make it unsuitable for routine prophylaxis against PPH. Oxytocin (Pitocin) or oxytocin combined with ergometrine (Syntometrine) therefore remain the preferred drugs for routine use in developed countries. Some trials have suggested that oxytocin alone is as efficacious as Syntometrine, whereas others have reported that it is not as effective. Intravenous ergometrine is associated with an increase in the incidence of retained placenta, possibly as a result of myometrial spasm distal to a fundally placed placenta leading to its forced retention, and should not be the agent of choice for routine administration. Ergometrine also causes peripheral vasoconstriction and a rise in blood pressure and should only be given with caution, if at all, to women with hypertension. Oxytocin, on the other hand, when given as an acute bolus, can cause a marked drop in blood pressure. Caution should therefore be exercised when giving oxytocin to women with cardiovascular problems, and a continuous low-dose infusion is probably preferable to bolus injection.1314 The active and passive management approaches represent the two extremes of the spectrum of common practice. Although the randomized controlled trials performed to date have only compared these two approaches, the benefits of early cord clamping and controlled cord traction in the prevention of PPH have not been established separately from the use of prophylactic uterotonic agents. It is from these two aspects that most criticisms of active management arise
Timing of Cord Clamping The umbilical cord can be clamped immediately after birth, clamped after pulsations cease, or left unclamped. The cord may need to be clamped before birth if there is tight nuchal entanglement. Although early clamping of the cord has been reported to be associated with significant shortening of the third stage, this has only been demonstrated in trials where no prophylactic oxytocin was given. The difference in the effects of early versus late cord clamping on the neonate are relatively minor, and opinions differ as to their relative risks and benefits. The deferral of cord clamping until 3 minutes after birth results in a neonatal transfusion of about 80 mL of blood from the placenta. This contributes about 50 mg of iron, which may reduce the frequency of iron-deficiency anemia later in childhood. The theoretical downsides of this blood transfusion are hypervolemia, polycythemia, hyperviscosity, and hyperbilirubinemia. In practice however, these have not been found to produce a clinically relevant increase in neonatal morbidity. The WHO review of evidence on management of the third stage concludes there is no clear evidence to favor one practice over the other. Delaying cord clamping until the pulsations stop is the physiological way of treating the cord and is not associated with adverse effects, at least in normal deliveries. Early cord clamping conflicts with traditional beliefs and is an intervention that needs justification. In preterm infants, delay in cord clamping has demonstrable benefits and has been shown to decrease the need for blood (P <0.001) and albumin (P <0.03) transfusions during the first 24 hours of life.2021
Controlled Cord Traction The use of cord traction has a long history, with the earliest records dating back to Aristotle. Simple cord traction was displaced in the 1800s by the introduction of the Credé maneuver. In this maneuver, the placenta is expelled by downward pressure on the fundus of the uterus in the direction of the birth canal, with the thumb placed on the posterior surface and the flat of the hand on the anterior surface of the fundus. This was proposed as an alternative means to manual removal for expelling the retained placenta and was found to avoid the uterine inversion that was occasionally associated with cord traction. Brandt in 1933 and Andrews in 1940 independently introduced similar methods to improve the use of cord traction to deliver the retained placenta. These involved traction on the cord with countertraction applied to the uterus abdominally. It was not until the 1960s, however, that the modern technique known as controlled cord traction was introduced by Spencer, accompanied by the routine administration of ergonovine.2223 The current consensus is that, when traction is applied to the umbilical cord, it should be done only during a uterine contraction while controlling the uterus by Brandt-Andrews maneuver to prevent uterine inversion. However, it should be noted that the benefits of both early cord clamping and the use of routine controlled cord traction to prevent PPH have not as yet been supported by evidence from randomized controlled trials.
Normal Third Stage of Labor Management OptionsQuality of EvidenceStrength of RecommendationReferencesActive management of third stage is advised for all women, and includes all the following:IaA Administer oxytocic agent (Pitocin (oxytocin) or Syntometrine (oxytocin and ergometrine) more commonly used than misoprostol).IbA Clamp and cut cord.—GPP— Use controlled cord traction (no randomized controlled data to show it reduces PPH rates of itself).IIIBTiming of cord clamping No evidence to indicate optimum timing in term delivery.IaA In preterm infants, delay in clamping may be of benefit.IIIBEnsure intravenous access for women at risk.—GPP—Save serum for rapid cross-match if needed, or actually cross-match 2 units, for women at risk.—GPP—
RETAINED PLACENTA Diagnosis and Definition Using a diagnostic cutoff of 30 minutes for a prolonged third stage, 42% of retained placentas deliver spontaneously within the next 30 minutes, with very few delivering spontaneously after 1 hour. Because the incidence of significant PPH rises after 30 minutes in the third stage, it therefore seems logical to institute some form of active intervention in an attempt to deliver the placenta between 30 and 60 minutes into the third stage. Dombrowski and colleagues noted that, compared with term pregnancies, the frequency of retained placenta (2.0% overall) was markedly increased among very preterm (gestation <27 weeks) and preterm pregnancies (gestation <37 weeks), with odds ratios of 20.8 and 3.0, respectively
Management Options Manual removal appears to be the management of choice for retained placenta. However, it is associated with a risk of infection (endometritis) and trauma (perforation of the uterine wall involved with the procedure). Ely and colleagues, in a retrospective study of 1052 manual removals, found that clinical endometritis developed in 6.7% of cases compared with only 1.8% following spontaneous placental delivery.26 In some studies, manual removal appears to be aggressively pursued, with rates exceeding 3% and often performed only 15 to 20 minutes into the third stage. The rate generally quoted internationally is 1% to 2%. In the absence of hemorrhage there is no urgency to resort to manual removal when less invasive alternatives are available. Patients with a prolonged third stage are often treated as a homogeneous group, although they have different clinical conditions. These include the retention of an already detached placenta (trapped placenta), an adherent placenta, and placenta accreta. Each condition should be distinguished from the others, and each requires a specific clinical approach. Herman notes that each of these conditions is associated with a different sonographic appearance, and concludes that "proper utilization of ultrasound may be crucial for optimal management."27
Trapped Placenta Trapped placenta often follows the intravenous administration of ergometrine when the onset of uterine contraction is very rapid. This tends to close the cervix at the same time as the placental detachment occurs, trapping the placenta. Intramuscular injection of ergometrine results in the onset of uterine contraction in 10 minutes, which is likely to follow rather than precede placental separation, so trapped placenta is less likely to occur. The clinical findings of a trapped placenta include a small, contracted fundus, with some vaginal bleeding and cord lengthening indicative of placental separation, and the placental margin may be palpable through the closed cervical os. On ultrasound examination the entire myometrium is thickened and a clear demarcation may be seen between it and the placenta.4 Delivery of a trapped placenta can usually be achieved using controlled cord traction, which encourages cervical dilation. Intravenous glyceryl trinitrate (100 to 200 µg) is useful as a short-term tocolytic agent, appears efficacious and safe, and may obviate the need for general anesthesia for uterine relaxation. Releasing the cord clamp, to allow blood trapped in the placenta to drain, may also help.28
Adherent Placenta With an adherent placenta, the uterine fundus remains broad and high and myometrial contractions may be weak or absent, but there is no bleeding while the placenta remains wholly attached. Adherent placenta is caused by a deficiency in the contractile force exerted by the myometrium underlying the placental site despite normal anatomy (i.e., it is not caused by pathologic invasion of the placenta into the uterine muscle, known as placenta accreta). On ultrasound the myometrium appears thick and contracted in all areas, except where the placenta remains attached, and the uterine wall remains less than 2 cm in thickness. If the placenta becomes partly separated the myometrium over the detached area appears thicker, but that underlying the adherent part remains thin (<2 cm). Detachment usually starts in the lower part of the uterus and is associated with bleeding from the placental bed. Treatment options depend on the amount of bleeding: In the absence of bleeding, a conservative approach can be adopted and manual removal of the placenta can be postponed while the problem is investigated (by ultrasound). Where there is active bleeding, immediate active management is necessary. Effective treatment of the adherent placenta is based on stimulating a contraction of the underlying myometrium that has sufficient strength to induce separation of the placenta. Oxytocin, ergonovine, and misoprostol are all capable of inducing sustained myometrial contractions. However, there is no evidence that systemic and repeated administration of either oxytocics or prostaglandins is able to assist in the delivery of the adherent placenta.4 5 Recent studies have shown that uterotonic agents administered via umbilical vein injection may be effective in causing the adherent placenta to separate, and this method is currently recommended as the first line of treatment by the WHO.29 The Pipingas technique has been shown effective in delivering drugs to the placental bed. A size 10 nasogastric tube is passed along the umbilical vein until resistance is felt, then retracted about 5 cm, and prostaglandin F2α (20 mg diluted in 20 mL of normal saline) or oxytocin (30 IU diluted in 20 mL of normal saline) is injected through the catheter.3031
Mechanisms of Labor in the Vertex Presentation The process of labor and delivery is marked by characteristic changes in fetal position or cardinal movements in relation to the maternal pelvis. These spontaneous adjustments are made to effect efficient passage through the pelvis as the fetus descends. Engagement is the descent of the largest transverse diameter, the biparietal diameter, to a level below the pelvic inlet. An occiput below the ischial spines is engaged. Descent of the head is a discontinuous process occurring throughout labor. Because the transverse diameter of the pelvic inlet is wider than the AP diameter, and because the greatest diameter of the unflexed fetal head is the AP diameter, in most instances the fetus enters the pelvis in an occiput transverse alignment. Flexion decreases the AP diameter of the fetal head. It occurs as the head encounters the levator muscle sling, thereby decreasing the diameter by approximately 1.5 to 2.5 cm (occipitomental, 12.0 cm, to occipitofrontal, 10.5 cm). Later, further flexion occurs, reducing the diameter to 9.5 cm (suboccipitobregmatic) (Fig. 2-10). Internal rotation occurs in the midpelvis. The architecture of the midpelvic passageway changes so that the AP diameter of the maternal pelvis at this level is greater than the transverse diameter. The fetus accommodates to this change by rotation of the head from a transverse orientation (occiput transverse) to an AP alignment (usually occiput anterior), thus accomplishing internal rotation. Further descent to the level of the perineum occurs with the head aligned in the AP plane. Extension of the head allows delivery of the head from the usual occiput anterior position through the introitus. Little actual descent occurs with extrusion of the head because the head is delivered by a reversal of the flexion that occurred as it entered the pelvis. The face appears over the perineal body, while the symphysis pubis acts as a fulcrum where it impinges on the occiput. External rotation occurs after delivery of the head, when the fetal head rotates back, or restitutes, toward the original transverse orientation (external rotation or restitution) when the bisacromial diameter (fetal shoulders) is aligned in an AP orientation with the
greatest diameter of the pelvic outlet. The remainder of the delivery proceeds with presentation of the anterior shoulder beneath the symphysis pubis and the posterior shoulder across the posterior fourchette (Fig. 2-10).