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INTRAPARTUM FETAL SURVEILLANCE 273
4. What parameters should be documented when electronic fetal monitoring is
used?
When reading a fetal heart tracing, it is important to make note of the following:
• Baseline
• Variability
• Presence or absence of accelerations
• Presence or absence of decelerations
5. What is meant by the term “baseline”?
The baseline is the mean fetal heart rate rounded to increments of 5 beats per minute (bpm) during a
10-minute segment. The baseline must be present for at least 2 minutes during this period; a change
lasting more than 2 minutes represents the establishment of a new baseline (not necessarily an accel-
eration or a deceleration).
6. What is a normal baseline, and what are some causes of baseline abnormalities?
A normal baseline is 110 to 160 bpm. Tachycardia is a baseline greater than 160 bpm, and it can be
caused by maternal infection (e.g., viral illness, pyelonephritis, or chorioamnionitis), a fetal arrhythmia,
or administration of drugs such as terbutaline. It can also be an early indication of fetal compromise.
Bradycardia is a baseline lower than 110 bpm, and it can be caused by maternal hypovolemia, fetal
heart block, and late or severe fetal compromise.
7. What is meant by the term “variability”?
Beat-to-beat variability is the small-scale oscillation of the baseline heart rate; it results from the
interplay between sympathetic and parasympathetic activity on the sinoatrial node. Variability is
characterized by the amplitude of the difference in peaks and troughs in beats per minute:
• Absent variability: No change in the amplitude occurs from beat to beat.
• Minimal variability: Change in amplitude is detectable, but less than 5 bpm.
• Moderate variability: Change in amplitude is 6 to 25 bpm; this is considered normal.
• Marked variability: Change in amplitude is greater than 25 bpm.
8. What can cause changes in variability?
Increased variability can be caused by fetal breathing or fetal movement. Decreased variability can
result from fetal acidemia, maternal administration of analgesic drugs, or maternal administration of
magnesium sulfate. Decreased variability is considered to be the most reliable warning sign of fetal
compromise, and it should always prompt heightened awareness and close surveillance.
9. What is meant by the term “acceleration”?
Accelerations are visually apparent increases in the fetal heart rate, and they are often associated with
fetal movement or stimulation. Before 32 weeks of gestation, the acceleration must be at least 10
bpm from the baseline and last 10 seconds or more. After 32 weeks of gestation, this increase must
be at least 15 bpm higher than the baseline and last 15 seconds or more.
10. What is meant by the term “deceleration”?
A deceleration is a visually apparent decrease in the fetal heart rate from an established baseline. The
four types of decelerations are early, late, variable, and prolonged.
11. What is an early deceleration?
Early decelerations are usually caused by fetal head compression during active labor. They are char-
acterized by a gradual decrease in the fetal heart rate, and they last 30 seconds or more from onset to
nadir, which coincides with the peak of a uterine contraction (Fig. 62-2). These decelerations are not
associated with tachycardia, loss of variability, fetal hypoxia, academia, or low Apgar scores.
12. What is a late deceleration?
Late decelerations indicate decreased oxygen delivery to the fetus secondary to uteroplacental insuffi-
ciency, maternal hypotension, excessive uterine activity, or placental abruption. Similar to early decelera-
tions, they are characterized by a gradual decrease in fetal heart rate lasting 30 seconds or more from
onset to nadir (Fig. 62-3). Unlike early decelerations, the nadir occurs after the peak of a contraction.
13. What is a variable deceleration?
Variable decelerations are caused by umbilical cord compression. They are characterized by an abrupt
decrease in the fetal heart rate, and they reach a nadir in less than 30 seconds. The decrease is 15
bpm or more and lasts between 15 seconds and 2 minutes (Fig. 62-4).
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274 LABOR, DELIVERY, AND POSTPARTUM
210
100
12
10
8
6
4
2
0 kPa
75
50
25
UA 0 mm Hg
100
12
10
8
6
2
0 kPa
75
50
25
UA 0 mm Hg
180
150
120
90
60
30
210
FH9 240 bpm FH9 240 bpm
180
150
120
90
60
30
Figure 62-2. Early decelerations. bpm, Beats per minute; FH, fetal heart rate; UA, uterine activity. (From Bashore RA,
Koos BJ. Fetal surveillance during labor. In: Hacker NF, Gambone JG, Hobel CJ, eds. Hacker and Moore’s Essentials of
Obstetrics and Gynecology. 5th ed. Philadelphia: Elsevier; 2010. )
210
180
150
120
90
60
30
FH9 240 bpm
210
FH9 240 bpm
180
150
120
90
60
30
12
10
8
6
4
2
100
75
50
25
UA 0 mm Hg0 kPa
12
10
8
6
4
2
0 kPa
Figure 62-3. Late decelerations. bpm, Beats per minute; FH, fetal heart rate; UA, uterine activity. (From Bashore RA,
Koos BJ: Fetal surveillance during labor. In: Hacker NF, Gambone JG, Hobel CJ, eds. Hacker and Moore’s Essentials of
Obstetrics and Gynecology. 5th ed. Philadelphia: Elsevier; 2010.)
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INTRAPARTUM FETAL SURVEILLANCE 275
14. What is a prolonged deceleration?
Prolonged decelerations are caused by sustained interruption of oxygen delivery to the fetus. They can
result from uterine tachysystole, placental abruption, tightening of umbilical cord knots, umbilical cord
prolapse, maternal shock, maternal hypoxia, or maternal hypotension. (Fig. 62-5). They are character-
ized by a decrease in the fetal heart rate of 15 bpm or more and last between 2 and 10 minutes; any
deceleration lasting longer than 10 minutes is considered a baseline change.
Prolonged decelerations are associated with fetal death if they are not managed appropriately.
15. What is a sinusoidal fetal heart rate pattern?
A sinusoidal pattern is a smooth, sine wave–like undulation of the fetal heart rate. It has regular oscil-
lations with an amplitude between 5 and 15 bpm around a fixed baseline anywhere between 120 and
160 bpm. The cycle frequency is two to five cycles/minute, and both variability and accelerations are
absent. This pattern can occasionally be seen following maternal use of intravenous opioids for pain
control (e.g., meperidine, butorphanol, and nalbuphine).
A true sinusoidal pattern not associated with maternal medication is an ominous finding and can be
associated with severe fetal hypoxia and acidemia. It has also been reported in cases of severe fetal ane-
mia secondary to causes such as intracranial hemorrhage, Rh alloimmunization, or bleeding vasa previa.
Figure 62-4. Variable deceleration. (From Westgate JA, Wibbens B, Bennet L, Wassink G, Parer JT, Gunn AJ. The
intrapartum deceleration in center stage: a physiologic approach to the interpretation of fetal heart rate changes in labor.
Am J Obstet Gynecol. 2007;197:236.e1-236.e11.)
Figure 62-5. Prolonged deceleration. (From Ugwumadu A. Understanding cardiotocographic patterns associated with
intrapartum fetal hypoxia and neurologic injury. Best Pract Res Clin Obstet Gynaecol. 2013;27:509-536.)
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276 LABOR, DELIVERY, AND POSTPARTUM
16. What is the three-tiered fetal heart rate interpretation system?
To help guide management, fetal heart tracings are placed into three categories based on their
characteristics (Table 62-1). Category I is considered normal, category II is indeterminate, and
category III is abnormal. The presence of one criterion from a higher category necessarily places the
fetus into that category. For example, if the fetal heart rate baseline is 110 to 160 bpm with moderate
variability, accelerations, and a prolonged deceleration, the tracing is considered to be category II
because of the prolonged deceleration.
17. How are category I fetal heart tracings managed?
Patients can be managed with either continuous electronic monitoring or intermittent auscultation.
18. How are category II fetal heart tracings managed?
Because category II includes a wide spectrum of patterns, several different interventions may be
helpful in reverting category II to category I tracings (Table 62-2).
Table 62-1. Category Classification Based on Fetal Heart Tracing
CATEGORY BASELINE VARIABILITY ACCELERATIONS
LATE OR
VARIABLE
DECELERA-
TIONS
EARLY
DECELERA-
TIONS
Category I 110-160 bpm Moderate Present or absent Absent Present or
absent
Category II Bradycardia
with
variability
Tachycardia
Minimal
Absent, with
no recurrent
decelerations
Marked
Absent, even after
fetal stimulation
Recurrent late
or variable
decelerations
with some
variability
Prolonged
decelerations
Absent
Category III Bradycardia
without
variability
Sinusoidal
pattern
Absent with
recurrent
decelerations
Absent Present without
variability
Absent
bpm, Beats per minute.
Table 62-2. Interventions for Common Category II Findings
FINDING ETIOLOGY INTERVENTIONS RATIONALE
Variable
decelerations
Umbilical cord
compression
1. Change maternal
position
2. Amnioinfusion
1. Move fetus off cord
2. Increase fluid around fetus to
relieve compression
Late
decelerations
Uteroplacental
insufficiency
1. Change maternal
position
2. Fluid bolus
3. Supplemental oxygen
4. Decrease/turn off
Pitocin
5. Tocolytic (terbutaline)
1. Decrease pressure on inferior
vena cava
2. Relieve maternal hypotension
3. Increase maternal oxygenation
4. Resolve tachysystole
5. Stop contractions; relieve
tetanic contractions
Tachycardia Maternal infection 1. Antibiotics
2. Heightened surveil-
lance
1. Treat infection
2. Evaluate for signs of fetal
compromise, such as placental
abruption or fetal bleeding
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INTRAPARTUM FETAL SURVEILLANCE 277
19. What is amnioinfusion?
Amnioinfusion is the introduction of fluid into the uterus to relieve umbilical cord compression after
fetal membranes have been ruptured. Although protocols can vary, they all involve placement of an
intrauterine catheter, an initial bolus of fluid, and subsequent infusion at a steady rate (frequently 2 to
3 mL/minute). Either normal saline or lactated Ringer solution is acceptable.
20. How are category III fetal heart tracings managed?
Because of their association with acidemia and poor neonatal outcomes, category III tracings require
immediate attention. If resuscitative interventions are successful and the tracing reverts to category I
or II, labor may proceed with heightened surveillance. If resuscitative interventions fail, delivery should
be expedited (often by cesarean section).
21. What are the other methods of intrapartum fetal surveillance?
Table 62-3 is an overview of ancillary methods of intrapartum fetal surveillance.
Table 62-3. Ancillary Methods of Intrapartum Fetal Surveillance
METHOD DESCRIPTION EVIDENCE COMMENTS
Fetal pulse oximetry Evaluates fetal
oxyhemoglobin
saturation
No change in cesarean rates
No difference in outcomes
Not used outside of
research
Fetal scalp sampling Assesses blood pH to
identify or confirm
fetal acidemia
Slight decrease in cesarean
rates
Rarely used because
of difficulty
obtaining and
analyzing an
adequate sample
Fetal
electrocardiography
Known ST-segment
and T-wave changes
occur with fetal
hypoxia
No change in cesarean
rates
No reduction in cases of
fetal acidemia
Not used outside
of research
Vibroacoustic
stimulation (VAS)
In nonacidotic
fetuses, fetal heart
rate accelerates in
response to VAS
Can predict fetal acidosis
in the setting of variable
decelerations, but not late
decelerations
Currently used in
clinical practice
FINDING ETIOLOGY INTERVENTIONS RATIONALE
Prolonged
decelerations,
fetal
bradycardia
Cord prolapse,
rapid fetal
descent,
tachysystole
1. Examine for umbilical
cord
2. Noninvasive
resuscitation
3. Terbutaline
4. If no resolution,
immediate delivery
1. Rule out cord prolapse
2. Increase uteroplacental
perfusion as above
3. Stop contractions
4. Prolonged fetal bradycardia,
especially with minimal
variability or absent variability,
is a sign of impending fetal
compromise
Minimal
variability
Fetal sleep cycle,
uteroplacental
insufficiency
1. Expectant management
2. VAS, scalp stimulation
3. Noninvasive
resuscitation
1. Sleep cycles last 20-60
minutes
2. Wake fetus if in a sleep cycle
3. Increase uteroplacental
perfusion
VAS, Vibroacoustic stimulation.
Table 62-2. Interventions for Common Category II Findings (Continued)
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278 LABOR, DELIVERY, AND POSTPARTUM
22. What is the role of uterine monitoring in intrapartum fetal surveillance?
Placental perfusion is temporarily decreased during a contraction, which challenges fetal oxygen
reserves and may result in late decelerations. Monitoring uterine contractions can help identify the
type of decelerations present and determine the cause of an abnormal fetal heart tracing. For more
information on uterine monitoring, see Chapter 61.
BiBliography
1. American College of Obstetricians and Gynecologists. Intrapartum fetal heart rate monitoring: nomenclature,
interpretation, and general management principles. ACOG practice bulletin no. 106. Obstet Gynecol. 2009;114:192–202.
2. American College of Obstetricians and Gynecologists. Management of intrapartum fetal heart rate tracings. ACOG
practice bulletin no. 116. Obstet Gynecol. 2010;116:1232–1240.
3. Bashore R, Koos B. Fetal surveillance during labor. In: Hacker N, Gambone J, Hobel C, eds. Hacker and Moore’s
Essentials of Obstetrics and Gynecology. 5th ed. Philadelphia: Saunders; 2010:119–127.
4. Beckmann C, Ling F, Barzandsky B, et al. Obstetrics and Gynecology. 6th ed. Baltimore: Lippincott Williams & Wilkins;
2010.
5. Creasy R, Resnik R, Iams J, Lockwood CJ, Moore TR, eds. Creasy and Resnik’s Maternal-Fetal Medicine: Principles and
Practice. 6th ed. Philadelphia: Saunders; 2009.
6. Cunningham F, Leveno K, Bloom S, Spong C, Dash J. Williams Obstetrics. 24th ed. New York: McGraw-Hill; 2014.
7. Modanlou HD, Murata Y. Sinusoidal heart rate pattern: reappraisal of its definition and clinical significance. J Obstet
Gynaecol Res. 2004;30:169–180.
8. Ugwumadu A. Understanding cardiotocographic patterns associated with intrapartum fetal hypoxia and neurologic
injury. Best Pract Res Clin Obstet Gynaecol. 2013;27:509–536.
9. Westgate JA, Wibbens B, Bennet L, Wassink G, Parer JT, Gunn AJ. The intrapartum deceleration in center stage: a
physiologic approach to the interpretation of fetal heart rate changes in labor. Am J Obstet Gynecol. 2007;197:236.
e1–236.e11.
KEY POINTS: INTRAPARTUM FETAL SURVEILLANCE
1. The goals of intrapartum fetal surveillance are to identify fetal hypoxia or acidemia and intervene
early enough to prevent neurologic injury or death.
2. Accelerations are visually apparent increases in the fetal heart rate. After 32 weeks of gestation,
the minimum requirements are an increase of 15 bpm or more above baseline and a duration of
15 seconds or more.
3. Accelerations and moderate beat-to-beat variability on a fetal heart tracing are considered
reassuring.
4. A three-tiered system is used to categorize fetal heart rate and help guide management;
Category I is considered normal.
5. Repeat variable, late, and prolonged decelerations are abnormal. They should prompt noninvasive
interventions and heightened surveillance.
6. Monitoring uterine contractions can help identify the type of decelerations present and determine
the cause of an abnormal fetal heart tracing.
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279
1. What is a cesarean delivery (CD)?
A CD is an abdominal (as opposed to vaginal) delivery. The rate of CDs has dramatically increased over
recent decades, from 5% in 1970 to more than 30% in 2007; it is one of the most common surgical
procedures performed worldwide.
2. What are the indications for a CD?
The three most common indications are (1) labor dystocia, (2) nonreassuring fetal heart tracing, and
(3) fetal malpresentation. Other indications include the following:
• Fetal or placental indications
• Fetal anomaly that precludes vaginal delivery (e.g., large omphalocele, macrocephaly)
• Malpresentation (e.g., breech presentation, transverse lie)
• Fetal macrosomia (>4500 g in a diabetic woman or >5000 g in a nondiabetic woman)
• Placenta previa
• Vasa previa
• Placental abruption with nonreassuring fetal heart tracing
• Umbilical cord prolapse
• Maternal indications
• History of a classical CD or CD with a T-shaped incision
• History of more than two previous CDs
• History of myomectomy or significant uterine surgical intervention
• Inability to labor (e.g., severe cardiac disease in which the Valsalva maneuver should be avoided)
• Mechanical obstruction (e.g., uterine fibroids or pelvic mass obstructing the internal os)
• Infection (active or prodromal herpes, human immunodeficiency virus [HIV] infection with a viral
load >1000 copies/mL)
• Maternal request (elective)
• Worsening maternal illness requiring urgent or emergency delivery (e.g., HELLP [hemolysis,
elevated liver enzymes, low platelets] syndrome, preeclampsia with severe features)
3. How is a CD performed?
A CD begins with a low transverse skin incision; vertical incisions are used in a minority of cases. The
underlying layers of fat and fascia are incised and extended to accommodate the size of the infant. In
general, the rectus muscles are dissected off the fascia before entering the peritoneum.
Once the uterus is exposed, it is inspected to determine which type of uterine incision to use.
The most common choice is a transverse incision made across the lower uterine segment, referred
to as a “low transverse incision.” If the lower uterine segment is poorly developed (which can occur
in preterm deliveries) or the fetus is in a position that may render delivery difficult, a vertical incision
may be chosen.
Once the uterine incision is made, an amniotomy is performed if necessary, and the infant is delivered.
The umbilical cord is clamped and cut, and the infant is handed to a waiting pediatric or nursing team.
The placenta is delivered, and the uterine incision is closed with suture. After hemostasis is confirmed, the
abdominal incision is closed and the skin is reapproximated with suture or surgical staples.
4. What other types of uterine incisions may be used during a CD, and why?
• Classical incision: a vertical incision through the contractile portion of the uterus. The lower
margin may begin as low as the lower uterine segment, and the upper margin may cross the
CHAPTER 63
CESAREAN DELIVERY AND
VAGINAL BIRTH AFTER
CESAREAN DELIVERY
Erin C. Chong, MD
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280 LABOR, DELIVERY, AND POSTPARTUM
fundus. This incision is used in cases of preterm deliveries when the lower segment is poorly
developed, in the presence of an anterior placenta previa (to avoid disrupting the placental bed
before delivery of the infant), and with fetal malpresentation (i.e., transverse lie with the back
oriented toward the cervix).
• Low vertical incision: This begins within the lower uterine segment and ends at a point below the
insertion of the round ligaments. This incision is chosen for similar reasons as a classical incision,
but it attempts to preserve the potential for vaginal delivery in subsequent pregnancies. Extending
the incision upward and converting it into a classic incision may be necessary.
• T-shaped incision: This occurs after a low transverse incision is made and found to be inadequate
for delivery of the infant; the myometrium is incised upward as high into the uterus as needed to
allow for delivery.
5. What are the potential complications of a CD?
The most common complications are the same as those for most major surgical procedures. They
include pain, infection, bleeding, and injury to adjacent organs. An estimated blood loss up to 1000 mL
is considered normal, and transfusions (with their own associated risks) are not uncommon. A risk of
intraoperative fetal injury also exists. Less common complications include venous thromboembolism,
pulmonary embolism, adverse reaction to anesthesia, ileus, and small bowel obstruction. Rarely, a
hysterectomy must be performed because of uncontrollable bleeding or placenta accreta (known or
unexpected). Other uncommon complications include maternal or fetal death, which can also occur in
vaginal deliveries.
A long-term risk associated with CD is a higher rate of complications in future pregnancies. A
history of a previous CD increases blood loss and operative time in subsequent CDs, conveys the risk
of uterine rupture during an attempted vaginal delivery, and increases the risk of abnormal placenta-
tion (placenta previa, accreta, or increta; for more information on this topic, see Chapter 66).
6. What are the risks and benefits of CD versus vaginal delivery?
Both CDs and vaginal deliveries have risks. Overall, CDs have a higher rate of maternal morbidity
(9.2% for CD versus 8.6% for vaginal delivery). These morbidities include wound infection, hematoma,
hemorrhage requiring transfusion, hysterectomy, venous thromboembolism, and longer hospital stay.
However, women who had vaginal deliveries are more likely to develop pelvic organ prolapse and
urinary incontinence compared with those who had CDs.
With respect to fetal risks, shoulder dystocia complicates approximately 1% to 3% of vaginal
deliveries and 0% of CDs. Brachial plexus injuries, however, can still occur before or during CD. Infants
delivered by CD without preceding labor are more likely to experience respiratory distress.
Maternal mortality is higher for CDs compared with vaginal delivery (13.3 in 100,000 vs. 3.6 in
100,000, respectively); vaginal delivery is recommended over CD, particularly in women who plan to
have multiple pregnancies.
7. Can CDs be performed by maternal request in the absence of maternal or fetal
indications?
Yes. CDs on maternal request comprise an estimated 2% of all CDs in the United States. To avoid neo-
natal risks associated with early term delivery, these CDs are performed at or after 39 weeks of gesta-
tion. Reasons given by patients who request a CD include fear of pain during childbirth, convenience,
negative past experiences in labor, concerns for long-term changes in pelvic floor function (e.g., pelvic
organ prolapse, incontinence), and concern for fetal well-being. Providers must be sure that these
women have been adequately counseled on the risks and benefits of both modes of delivery.
8. Does having one CD commit a woman to having CDs for all subsequent
pregnancies?
No. As long as the previous uterine incision did not extend into the contractile portion of the uterus, a
trial of labor after cesarean (referred to as TOLAC) may be considered.
9. What is the difference between a TOLAC and vaginal birth after cesarean (VBAC)?
A TOLAC refers to the attempt at a vaginal delivery. It may result in either a vaginal birth (VBAC) or a
repeat CD (i.e., failed TOLAC).
10. What are the benefits of VBAC compared with repeat CD?
• Faster recovery time
• Avoidance of a major surgical procedure
• Improved infant outcomes
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CESAREAN DELIVERY AND VAGINAL BIRTH AFTER CESAREAN DELIVERY 281
• Lower blood loss
• Lower chance of abnormal placentation in future pregnancies
11. What are the risks of TOLAC compared with repeat CD?
Both TOLAC and repeat CD are associated with risks of hemorrhage, infection, thromboembolic
disease, uterine rupture, and even maternal and fetal death. However, most of the morbidity
surrounding a TOLAC is associated with the need for an eventual CD; compared with an elective
repeat CD, a failed TOLAC has a higher complication rate.
12. What is uterine rupture, and how is it managed?
Uterine rupture is the separation of the layers of the uterine wall that results in a direct communica-
tion between the uterine and abdominal cavities. Potential sequelae include placental abruption,
hemorrhage requiring transfusion, hysterectomy, fetal neurologic injury from hypoxia, and fetal death.
Uterine rupture is an obstetric emergency; once it is suspected, an emergency CD should be
performed as quickly and safely as possible. Obstetric, anesthesia, pediatric, and nursing teams
should all be made aware of the situation. Blood products should be ordered and readily available.
13. What are the signs and symptoms of uterine rupture?
• Nonreassuring fetal heart tracing
• Loss of fetal station
• Sudden severe abdominal or supraclavicular pain
• Heavy vaginal bleeding
• Maternal hemodynamic instability
14. What are risk factors for uterine rupture, and what are the rates associated with
each?
Table 63-1 provides an overview of risk factors for uterine rupture.
15. What characteristics make a patient more likely to have a successful TOLAC?
Factors that increase the likelihood of success include a history of a previous vaginal delivery or VBAC
and the onset of spontaneous labor (as opposed to labor induction).
16. What characteristics make a patient less likely to have a successful TOLAC?
TOLAC success rates are lower for women who are obese, are older than 35 years of age, have
preeclampsia, have a macrosomic fetus, are not of white ethnicity, and are at more than 40 weeks of
gestational age. Success is also less likely for women with a history of CD for labor dystocia.
17. What are contraindications to TOLAC?
Any features that preclude vaginal delivery also preclude TOLAC. Other contraindications reflect
an unacceptably high risk of uterine rupture: more than two earlier CDs, history of a classical or
T-shaped uterine incision, history of uterine rupture in a previous TOLAC, or history of significant
uterine surgical intervention (e.g., transfundal uterine surgical procedure, repair of develop-
mental anomaly). With the exception of having more than two previous CDs, patients with these
contraindications should be delivered by repeat CD before the onset of labor (usually 37 to 38
weeks of gestation).
Table 63-1. Risk Factors for Uterine Rupture and Their Associated Rates
RISK FACTOR RATE OF RUPTURE
One prior low transverse uterine incision <1%
One prior low vertical uterine incision <1%
Two prior low transverse uterine incisions <2%
Labor induction or augmentation ∼1%
Short interpregnancy interval (<18 months) 4.8%
Prior classic or T-shaped uterine incision 4%-9%
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282 LABOR, DELIVERY, AND POSTPARTUM
18. Can women attempting TOLAC undergo induction of labor?
Yes. Although rates of uterine rupture associated with induction of labor (without use of prostaglandins)
are greater than rates in women who present in spontaneous labor, this risk is still approximately 1%.
Augmentation with oxytocin also increases the risk of rupture, but this risk is also approximately 1%.
Prostaglandins are not recommended for induction of labor in women with a previous CD
because of the increased risk of uterine rupture (>2%).
19. Can TOLAC be attempted in twin pregnancies?
Yes. For more information about vaginal delivery of twins, see Chapter 60.
20. What about patients who desire an elective or elective repeat CD but have a
pregnancy with poor dating?
Two options exist for these patients: (1) await an indication for delivery (spontaneous labor, rupture
of membranes, abnormal fetal surveillance) or (2) perform amniocentesis to assess for fetal lung
maturity. For more information on adequate pregnancy dating, see Chapter 38.
21. How is fetal lung maturity assessed?
Amniocentesis is performed using ultrasound guidance, and then the sample of amniotic fluid
is tested for signs of lung maturity by using either biochemical or biophysical tests. These tests
include the lecithin-to-sphingomyelin ratio, lamellar body count, and testing for the presence of
phosphatidylglycerol (Table 63-2).
BiBliography
1. American College of Obstetrics and Gynecologists. Vaginal birth after previous cesarean delivery. ACOG practice
bulletin no. 115. Obstet Gynecol. 2010;116:1143–1156.
2. American College of Obstetricians and Gynecologists. Cesarean delivery on maternal request. ACOG committee
opinion no. 559. Obstet Gynecol. 2013;121:904–907.
3. American College of Obstetricians and Gynecologists. Society for Maternal-Fetal Medicine, Caughey AB, Cahill AG,
Guise JM, Rouse DJ. Safe prevention of the primary cesarean delivery. Am J Obstet Gynecol. 2014;210:179–193.
4. Bujold E, Gauthier RJ. Risk of uterine rupture associated with an interdelivery interval between 18 and 24 months.
Obstet Gynecol. 2010;115:1003–1006.
Table 63-2. Tests Used to Determine Fetal Lung Maturity
TEST POSITIVE VALUE COMMENTS
Lecithin-to-sphingomyelin
ratio (L/S ratio)
2:1 Affected by blood and meconium
Lamellar body count (LBC) 50,000 lamellar bodies/μL Affected by blood, meconium,
and severe polyhydramnios
Phosphatidylglycerol (PG) Present Not affected by blood or meconium
KEY POINTS: CESAREAN DELIVERY AND VAGINAL BIRTH
AFTER CESAREAN
1. A CD is one of the most common surgical procedures performed worldwide, and it usually involves a
transverse incision in the lower segment of the uterus.
2. The three most common indications for a CD are labor dystocia, nonreassuring fetal heart tracing,
and malpresentation.
3. Compared with vaginal deliveries, CDs have higher rates of maternal morbidity and mortality. A
long-term risk associated with CD is a higher rate of complications in future pregnancies.
4. As long as a patient has not had more than two CDs and any previous uterine incisions did not
extend into the contractile portion of the uterus, a TOLAC may be considered.
5. A successful TOLAC is associated with fewer maternal and neonatal complications compared with a
scheduled repeat CD. However, a scheduled repeat CD has fewer complications than a failed TOLAC.
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