Fragile X syndrome is an X-linked disorder that causes mental retardation. It is caused by a repeat in the
6. External rotation or restitution 7. Expulsion
occurs in 95% of term labors, the cardinal movements of labor are defined relative to this presentation. To accommodate to the maternal bony pelvis, the fetal head must undergo several movements as it passes through the birth canal. These movements are accomplished by means of the forceful con-tractions of the uterus. These cardinal movements of labor do not occur as a distinct series of movements, but rather as a group of movements that overlap as the fetus accommo-dates and moves progressively through the birth canal.
These movements are 1. Engagement 2. Flexion 3. Descent
4. Internal rotation
(A) (B)
(C) (D)
(E) (F)
FIGURE 8.6. Cardinal move-ments of labor: engagement (A), flexion (B), descent (C), internal rotation (D), extension (E), and external rotation (F).
maneuvers require it. Supine labor is common in the United States. The left lateral position keeps the uterus off the infe-rior vena cava; this obstructs venous return, thence cardiac output, leading to hypotension (supine hypotensive syn-drome). The dorsal lithotomy position is most commonly used for spontaneous and operative vaginal delivery in the United States. Elsewhere in the world, many other laboring posi-tions are common, including sitting or crouching, in special
“birthing chairs,” on labor balls, or in variously configured tubs of warm water.
FLUIDMANAGEMENT ANDORALINTAKE
Because labor is associated with decreased gastrointestinal peristalsis, there is concern about aspiration during the administration of anesthesia. Patients in active labor should
avoid oral ingestion of anything except clear fluids (sips only), occasional ice chips, and preparations for moisten-ing the mouth and lips.
When oral intake is not possible or is insufficient, intravenous therapy with 1⁄2normal saline or D5 1⁄2normal saline is indicated. Normal saline can be used if increased oncotic pressure is desired, but lactated fluids are gener-ally contraindicated because of the metabolic acid deficit incurred by the lactate administration.
EVALUATION OFFETALWELL-BEING
Measurement of the fetal heart rate and its changes dur-ing labor is the primary means of intrapartum assessment of fetal well-being. This may be done by intermittent aus-cultation with a stethoscope or hand-held Doppler, or by the use of electronic fetal monitoring. The method chosen may depend on risk assessment at admission, the prefer-ence of the patient and the obstetric staff, and department policy. Risk factors include vaginal bleeding, acute abdom-inal pain, temperature >100.4°F, preterm labor or rupture of membranes, hypertension, and nonreassuring fetal heart rate pattern.
In the absence of risk factors on admission, the standard approach to fetal monitoring is to determine, evaluate, and record the fetal heart rate every 30 minutes in the active phase in the first stage of labor, and at least every 15 minutes in the second stage. In the presence of risk factors, fetal sur-veillance should be performed using either intermittent aus-cultation or continuous fetal monitoring. During the active first stage of labor, auscultation should be performed every 15 minutes, preferably before, during, and after a contrac-tion, and continuous monitoring should be evaluated at least every 15 minutes. During the second stage of labor, the fetal heart rate should be monitored every 5 minutes using either the intermittent or continuous procedure. If electronic fetal monitoring is used, an external tocodynamometer is initially used to assess uterine activity, providing information regard-ing the frequency and duration of contractions, but not their intensity. Electronic fetal monitoring is not necessary for a low-risk term pregnancy.
Control of Pain
Management of discomfort and pain during labor is an essential part of good obstetric practice. Some patients tolerate pain by using techniques learned in childbirth preparation programs. It is important that bedside staff be knowledgeable about these pain management techniques and be supportive of the patient’s decisions. Unless con-traindicated, pharmacologic analgesics to ameliorate pain of contractions should be made available on request to women in labor.
During the first stage of labor, pain results from the contraction of the uterus and dilation of the cervix. This pain travels along the visceral afferents, which accompany
sympathetic nerves entering the spinal cord at T-10, T-11, T-12, and L-1. As the fetal head descends, there is also dis-tension of the lower birth canal and perineum. This pain is transmitted along somatic afferents that comprise por-tions of the pudendal nerves that enter the spinal cord at S-2, S-3, and S-4. To provide relief from obstetric pain, the following methods of anesthesia and analgesia are used.
• Epidural block: infusion of local anesthetics or narcotics through a catheter into the epidural space. The most effective form of intrapartum pain relief in the United States, it can be used in either vaginal or abdominal deliv-eries and in postpartum procedures such as tubal ligation.
• Spinal anesthesia: a single injection of anesthetic
• Combined spinal–epidural: combination of the above two techniques
• Local block: local injection of anesthetic into the perineum or vagina. A pudendal block is a local block (Fig. 8.7).
• General anesthesia: inhaled or intravenous administra-tion of anesthetic agents that results in a loss of mater-nal consciousness. This technique is reserved only for cesarean deliveries in selected cases.
To determine which method of obstetric pain control should be used, the positive and negative aspects of each should be considered. Of the regional modes of analgesia, epidural anesthesia is superior to spinal anesthesia in that it can be left as a continuous source of analgesia and anesthe-sia during both the labor and delivery process. The advan-tage of this technique is its ability to provide analgesia during labor as well as excellent anesthesia for delivery, yet main-tain the patient’s sense of touch, facilitating participation in the birth process. Spinal anesthesia provides good pain relief for procedures of limited duration, such as cesarean delivery or vaginal delivery when labor is rapidly progressing.
Combined spinal–epidural anesthesia has advantages:
the epidural catheter to titrate medications throughout labor and the rapid onset associated with spinal techniques.
All of these types of regional anesthesia may be associated with a postdural puncture headache. However, combined spinal–epidural anesthesia avoids the risk of spinal headache in the mother and reduces the risk of sympathetic blockade, which could lead to hypotension. There is also less motor blockade than with spinal anesthesia. Local block may pro-vide anesthesia for episiotomy and repair of vaginal and per-ineal lacerations; however, paracervical block may result in fetal bradycardia. General anesthesia is associated with complications such as maternal aspiration and neonatal depression. If properly administered, it is effective for most cesarean deliveries, but regional anesthesia is preferable.
Management of Labor FIRSTSTAGE
Evaluation of the progress of labor is accomplished by means of a series of pelvic examinations. At the time of
each vaginal examination, a sterile lubricant is used. Each examination should identify cervical dilation, effacement, station, position of the presenting part, and the status of the membranes. These findings should be noted graphi-cally on the hospital record, so that abnormalities of labor may be identified. During the latter portions of the first stage of labor, patients may report the urge to push. This may indicate significant descent of the fetal head with pressure on the per-ineum. More frequent vaginal examinations during this time may be necessary. Similarly, if there are significant fetal heart rate decelerations, more frequent examinations may be necessary to determine whether the umbilical cord is pro-lapsed or if delivery is imminent.
In addition to rupturing the membranes to insert an intrauterine pressure catheter or a fetal scalp monitor, if needed, artificial rupture of membranes many be bene-ficial in other ways. The presence or absence of meco-nium (fetal stool) can be identified. However, rupture of the membranes does carry some risk, because the inci-dence of infection may be increased if labor is prolonged, or umbilical cord prolapse may occur if rupture of the membranes is undertaken before engagement of the pre-senting fetal part. Spontaneous rupture of membranes has similar risks. The fluid should be observed for meconium and blood. Fetal heart tones should be assessed after mem-branes spontaneously rupture.
SECONDSTAGE
Once the second stage of labor has been reached (i.e., com-plete cervical dilation to 10 cm), voluntary maternal effort (pushing) can be added to the involuntary contractile forces of the uterus to facilitate delivery of the fetus. With the onset of each contraction, the mother is encouraged to inhale, hold her breath, and perform an extended Valsalva maneuver. This increase in intra-abdominal pressure aids in fetal descent through the birth canal.
It is during the second stage of labor that the fetal head may undergo further alterations. Molding is an alteration in the relation of the fetal cranial bones, even resulting in par-tial bone overlap (Fig. 8.8). Some minor degree of molding is common as the fetal head adjusts to the bony pelvis. The greater the disparity between the fetal head and the bony pelvis, the greater the amount of molding. Caput succeda-neum is the edema of the fetal scalp caused by pressure on the fetal head by the cervix. Molding and caput succedaneum are the two most common causes of overestimation of the amount of descent, that is, of station. When there is a large amount of space “between the back of the fetal head and the curve of the sacrum,” the physician is alerted to the possibility that the biparietal diameter of the fetal head is higher than might be thought based upon the physical level to which the presenting part’s farthest dimension has reached. An
Ischial spine
Pudendal nerve
Sacrospinous ligament FIGURE 8.7. Pudendal block. Local
anes-thesia can be administered easily at the time of delivery to provide perineal anes-thesia for a vaginal delivery.
tissues and facilitate extension of the head, a modified Ritgen maneuver is performed (Fig. 8.10). This maneu-ver involves placing one hand omaneu-ver the maneu-vertex while the other hand exerts pressure through the perineum onto the fetal chin. A sterile towel is used to avoid contamination of this hand by contact with the anus. The chin can then be delivered slowly, with control applied by both hands.
After delivery of the head, the shoulders descend and rotate to a position in the anteroposterior diameter of the pelvis. The attendant’s hands are placed on the chin and vertex, applying gentle downward pressure, thus deliver-ing the anterior shoulder. To avoid injury to the brachial plexus, care is taken not to put excessive force on the neck.
The posterior shoulder is then delivered by upward trac-tion on the fetal head (Fig. 8.11). Delivery of the body now occurs easily in most cases. Immediately after delivery, the uterus significantly decreases in size.
Third Stage
Delivery of the placenta is imminent when the uterus rises in the abdomen, becoming globular in configuration, indi-cating that the placenta has separated and has entered the lower uterine segment; a gush of blood and/or “lengthen-ing” of the umbilical cord also occur. These are the three classic signs of placental separation. Pulling the placenta FIGURE 8.8. Molding of head.
Mediolateral episiotomy
Midline episiotomy
FIGURE 8.9. Episiotomy.
extended second stage may last as long as 2 to 3 hours, and the prolonged resistance encountered by the fetal vertex may prevent appropriate identification of fontanels and sutures. Both caput and molding resolve in the first few days of life. If identified before the second stage of labor, these changes should be noted on the pelvic examination and may indicate a potential problem in negotiation of the birth canal.
An episiotomy facilitates delivery by enlarging the vaginal outlet and may be indicated in cases of instrumen-tal delivery and/or protracted or arrested descent. With progressive labor and control of the fetal head and body at delivery, the risk of obstetric laceration with a normal-sized infant is low, so that the need for episiotomy is mini-mal. If an episiotomy is needed, it should be performed only after the perineum has been thinned considerably by the descending fetal head, and the incision should be somewhat longer on the mucosal as compared to the perineal surface of the incision (Fig. 8.9).
As the fetal head crowns (i.e., distends the vaginal opening), it is delivered by extension to allow the smallest diameter of the fetal head to pass over the perineum. This natural mechanism decreases the likelihood of laceration or extension of an episiotomy. To support the perineal
FIGURE 8.10. Vaginal delivery with midline episiotomy assisted by modified Ritgen maneuver.
from the uterus by excessive traction on the cord should be avoided. Inappropriate application of force may result in inversion of the uterus, an obstetric emergency associated with profound blood loss and shock. Instead, it is appropri-ate to wait for spontaneous extrusion of the placenta, some-times up to 30 minutes. As the placenta passes into the lower uterine segment, gentle downward pressure is applied to the fundus of the uterus, and the placenta is guided by very gen-tle traction on the umbilical cord (Fig. 8.12). If necessary, the placenta may be removed manually. This is accomplished by passing a hand into the uterine cavity and using the side of the hand to develop a cleavage plane between the placenta and the uterine wall. Anesthesia may be required. The umbilical cord should be evaluated for the presence of the expected two umbilical arteries and one umbilical vein.
After the placenta has been removed, the uterus should be palpated to ensure that it has reduced in size and become firmly contracted. Excessive blood loss at this or any subsequent time should suggest the possibility of uterine atony. The use of uterine massage as well as oxytocic agents such as oxytocin, methylergonovine maleate (Methergine), or prostaglandins (carboprost or misoprostol) may be used routinely in the circumstance of excessive postpartum blood loss.
Inspection of the birth canal should be performed in a sys-tematic fashion. The introitus, vagina, perineum, and the vulvar area, including the periurethral area, should be evaluated for lacerations. Ring forceps are commonly used to hold and evaluate the cervix. Lacerations, if present, are most commonly found at the 3 o’clock and
9 o’clock positions of the cervix. Repair is accomplished with an absorbable suture. Obstetric lacerations are clas-sified in Table 8.2.
Fourth Stage
For the first hour after delivery, the likelihood of serious post-partum complications is at its greatest. Postpost-partum uterine hem-orrhage occurs in approximately 1% of patients. It is more likely to occur in cases of rapid labor, protracted labor, uter-ine enlargement (large fetus, polyhydramnios, multiple ges-tation), or intrapartum chorioamnionitis. Immediately after the delivery of the placenta, the uterus is palpated to deter-mine that it is firm. Uterine palpation is done in this period to ascertain uterine tone. Perineal pads are applied and the amount of blood on these pads as well as pulse and blood FIGURE 8.11. Delivery of anterior and posterior shoulders.
Classification of Obstetric Lacerations 8.2
T A B L E
FIGURE 8.12. Delivery of the placenta.
Degree of Laceration Description
First degree Involves the vaginal mucosa or perineal skin, but not the under-lying tissue
Second degree Involves the underlying subcuta-neous tissue, but not the rectal sphincter or rectal mucosa Third degree Extends through the rectal
sphincter, but not into the rectal mucosa
Fourth degree Extends into the rectal mucosa
pressure are monitored closely for the first several hours after delivery to identify excessive blood loss.
LABOR INDUCTION
Labor can be induced when the benefits to either the woman or the fetus outweigh those of continuing the pregnancy. Labor induction can be achieved with intra-venous oxytocin administration. The device used to administer oxytocin should permit precise control of the flow rate to ensure accurate, minute-to-minute control.
Various regimens exist for stimulation of uterine con-tractions. These regimens vary in initial dose, amount of incremental dose increase, and interval between dose increases. Lower and less frequent dosage increases are associated with a lower incidence of uterine hyperstimu-lation. Higher and more frequent dosage increases may result in shorter time in labor and reduce the incidence of chorioamnionitis and the number of cesarean deliveries performed for dystocia (abnormal labor), but also in increased rates of uterine hyperstimulation.
Cervical ripening may be beneficial if the cervix is unfavorable for induction. Several techniques are avail-able. Misoprostol, a prostaglandin E analog, is an effec-tive agent for cervical ripening and induction of labor.
It is administered vaginally. Prostaglandin E2 (PGE2) can also be administered vaginally or intracervically.
Because of the increased risk of uterine hyperstimula-tion, both drugs are contraindicated in patients who have had a previous cesarean delivery or previous uterine surgery.
Cervical ripening also can be accomplished with mechanical dilation with laminaria. Laminaria are hygro-scopic rods made from the stems of the seaweed Laminaria japonica that are inserted into the internal cervical os. As the rods absorb moisture and expand, the cervix is slowly dilated (Fig. 8.13). The risks associated with laminaria use include failure to dilate the cervix, cervical laceration, inadvertent rupture of the membranes, and infection. A synthetic form is also available. Placement of a 30 mL Foley catheter in the cervical canal is also used for cervi-cal ripening.
Induction of labor by “stripping” or “sweeping” the amniotic membranes is a relatively common practice. Risks associated with this procedure include infection, bleeding from an undiagnosed placenta previa or low-lying placenta, and accidental rupture of membranes. Artificial rupture of membranes is another method of labor induction that may be used, particularly when the cervix is favorable. Routine early amniotomy results in a modest reduction in the direc-tion of labor, but may result in an increased rate of intra-amniotic infection and cesarean delivery for fetal heart rate abnormalities. For these reasons, routine amniotomy is not recommended.
CESAREAN DELIVERY
Cesarean delivery is the most frequent major operation performed in the United States. Until 1965, the rate of cesarean delivery was stable at less than 5%, when it began to increase; it was more than 30% in 2005. Reasons for this increase include the ready availability of improved neonatal intensive care units in which infants with com-plications have a significantly greater survival rate, use in breech deliveries, and use in situations in which more sophisticated fetal monitoring is nonreassuring. How-ever, no major improvements in newborn outcomes have occurred as a result.
The decision regarding mode of delivery should be made by the health care provider together with the patient.
Advantages of a successful vaginal delivery include reduced risks of hemorrhage and infection; shorter postpartum hos-pital stay; and a less painful, more rapid recovery. However, cesarean delivery may be necessary. Examples of indications for cesarean delivery include hemorrhage from placenta previa, abruptio placentae, prolapse of the umbilical cord, and uterine rupture, as these conditions require prompt delivery. Planned vaginal delivery may be a reasonable approach for a fetus in breech presentation, but depends on the experience of the health care provider. In such circumstances, women should be informed that the risk of perinatal or neonatal mortality or short-term serious neonatal morbidity may be higher with a vaginal delivery than with a cesarean delivery, and the patient’s informed consent should be documented.
An estimated 2.5% of all births in the United States are cesarean delivery on maternal request. This procedure should not be performed before 39 weeks of gestation, unless lung maturity can be documented. It is not recom-mended for women desiring several children, because the
(A) (B)
FIGURE 8.13. Use of laminaria. (A) Laminaria properly inserted just beyond the cervical os. (B) Properly placed laminaria that has expanded, causing cervical dilation.
