monitoring fetal heart rate during labor

1. Military Maternity Hospital
D.Kahtan Sbeqi
29 November 2011

2. INTRODUCTION
 FHR patterns are indirect markers of the fetal cardiac
and medullary responses to blood volume changes,
acidemia, and hypoxemia,
 all obstetrical organizations advise monitoring the
FHR during labor
 A trial comparing auscultation with no monitoring
found that auscultation was associated with an
increased risk of operative delivery without any
reduction in perinatal mortality

3. EFFECTIVENESS OF INTRAPARTUM
FHR MONITORING
 The primary goal of FHR monitoring is to identify
hypoxemic and acidotic fetuses in whom timely
intervention will prevent death
 A secondary goal is to avoid fetal neurologic injury, if
possible
 The two commonly used modalities for intrapartum
FHR monitoring, continuous electronic FHR
monitoring and intermittent auscultation,

4. comparing these two techniques shows:
The intrapartum fetal death rate is approximately 0.5 per
1000 births with either approach
Apgar scores and neonatal intensive care unit admission
rates are similar for both modalities
Neither approach reduces the risk of long-term neurologic
impairment or cerebral palsy
 A major disadvantage of continuous electronic FHR
monitoring is that it leads to higher operative delivery rates
(cesarean delivery; instrumental vaginal delivery ) without
an associated neonatal benefit
 compared to intermittent auscultation, continuous
electronic FHR monitoring was associated with a two-fold
increase in risk of cesarean delivery performed because of a
nonreassuring FHR

5. INDICATIONS
 Routine electronic FHR monitoring for low-risk women in
labor is not recommended
 There is insufficient evidence to recommend for or against
intrapartum electronic FHR monitoring for high-risk
pregnant women.
 The American College of Obstetricians and Gynecologists
stated
 High risk pregnancies (eg, preeclampsia, suspected growth
restriction, type 1 diabetes mellitus) should be monitored
continuously during labor.
 Either electronic FHR monitoring or intermittent
auscultation is acceptable in uncomplicated patients.

6. EVALUATION OF THE FETAL HEART
RATE
National Institutes of Health guidelines for
interpretation of fetal heart tracings 2008
 Variability
Fluctuations in baseline that are irregular in amplitude and
frequency
Absent = amplitude undetectable
Minimal = amplitude 0 to 5 bpm
Moderate = amplitude 6 to 25 bpm
Marked = amplitude over 25 bpm
Measured in a 10 minute window. The amplitude is measured
peak to trough. There is no distinction between shortterm
and longterm variability.

7. Moderate variability

8.  Baseline rate
Bradycardia = below 110 bpm
Normal = 110 to 160 bpm
Tachycardia = over 160 bpm
The baseline rate is the mean bpm over a 10 minute
interval, excluding periodic changes, periods of
marked variability, and segments that differ by more
than 25 bpm. The baseline must be identifiable for 2
minutes during the interval (but not necessarily a
contiguous 2 minutes), otherwise it is considered
indeterminate.

9.  Acceleration
An abrupt* increase in the FHR. Before 32 weeks of gestation,
accelerations should last ≥10 sec and peak ≥10 bpm above
baseline. As of 32 weeks gestation, accelerations should last
≥15 sec and peak ≥15 bpm above baseline.
A prolonged acceleration is ≥2 minutes but less than 10
minutes. An acceleration of 10 minutes or more is
considered a change in baseline.

10.  Late deceleration
A gradual* decrease and return to baseline of the FHR
associated with a uterine contraction. The deceleration
is delayed in timing, with the nadir of the deceleration
occurring after the peak of the contraction. The onset,
nadir, and recovery usually occur after the onset, peak,
and termination of a contraction

11.  Early deceleration
A gradual decrease and return to baseline of the FHR
associated with a uterine contraction. The nadir of the FHR
and the peak of the contraction occur at the same time.
The deceleration's onset, nadir, and termination are usually
coincident with the onset, peak, and termination of the
contraction.

12.  Variable deceleration
An abrupt decrease in FHR below the baseline. The
decrease is ≥15 bpm, lasting ≥15 secs and <2 minutes
from onset to return to baseline. The onset, depth, and
duration of variable decelerations commonly vary with
successive uterine contractions

13.  Prolonged deceleration
A decrease in FHR below the baseline of 15 bpm or more,
lasting at least 2 minutes but <10 minutes from onset
to return to baseline. A prolonged deceleration of 10
minutes or more is considered a change in baseline.

14. Reassuring patterns
reassuring pattern indicates that there is minimal likelihood
of acidemia AT THAT POINT IN TIME:
 A baseline fetal heart rate of 110 to 160 bpm
 Absence of late or variable FHR decelerations
 Moderate FHR variability (6 to 25 bpm)
 Age appropriate FHR accelerations
 Early decelerations may or may not be present, FHR
accelerations are an important finding
 less than moderate variability does not reliably mean the
fetus is acidotic. In the absence of accelerations despite
scalp stimulation, fetal academia is present in about 50
percent of patients

15.  early decelerations are believed to be vagally mediated
and due to fetal head compression
 A baseline FHR of 100 to 110 follows the same
physiology; if it is persistent for more than an hour,
cephalopelvic disproportion may be present

16. Nonreassuring patterns
 Nonreassuring tracings (category III) are associated
with abnormal fetal acid-base status at the time of
observation
 Prompt evaluation of these patients is indicated and
prompt intervention (supplemental oxygen therapy,
change in position, treatment of hypotension,
discontinuation of any uterotonic drugs)

17. Nonreassuring patterns include:
1. Absent or minimal variability with decelerations or
bradycardia:
 is thought to be a result of cerebral hypoxemia and
acidosis
 Nonhypoxia-related causes include anencephaly and other
central nervous system defects, use of some centrally acting
drugs (eg, opiates, magnesium sulfate, atropine), sepsis,
defective cardiac conduction (eg, complete heart block),
and fetal sleep
Absent variability with any of the following FHR changes is
predictive of abnormal fetal acid-base status:
 Recurrent late decelerations
 Recurrent variable decelerations
 Bradycardia

18. 2. Sinusoidal heart rate pattern
 is defined as a pattern of regular variability resembling a
sine wave, with a fixed periodicity of three to five cycles per
minute, an amplitude of 5 to 40 bpm, and lasting for at
least 10 minutes
 response to moderate fetal hypoxemia, often secondary to
fetal anemia

19. MANAGEMENT OF FETAL HEART
RATE PATTERNS
Three tier approach : In 2008, the National Institutes of
Child Health and Human Development creating a three
tier FHR interpretation system
Category I
All of the following criteria must be present. these criteria are
predictive of normal fetal acid-base balance at the time of
observation.
 Baseline rate: 110-160 beats per minute (bpm)
 Moderate baseline FHR variability
 No late or variable decelerations
 Early decelerations may be present or absent
 Accelerations may be present or absent

20. Category III
Category III tracings are predictive of abnormal fetal acid-
base status at the time of observation. Prompt evaluation is
indicated and most parturients will require expeditious
intervention, such as provision of supplemental oxygen,
change in position, treatment of hypotension, and
discontinuation of any uterotonic drugs being
administered.
(1) Absent baseline FHR variability and any of the following:
• Recurrent late decelerations
• Recurrent variable decelerations
• Bradycardia
(2) Sinusoidal pattern
category II : FHR tracing does not meet criteria for either
category I or III and is considered indeterminate

21. Further evaluation of
nonreassuring patterns
FHR response to stimulation : fetal scalp stimulation
maneuver is easy to perform, inexpensive, readily
available, and not uncomfortable
 If a FHR acceleration is elicited (rise of ≥15 bpm above
baseline lasting for ≥15 seconds), absence of acidosis
(ie, fetal pH greater than 7.20) is likely
 when accelerations are induced by scalp stimulation,
acidosis is present in less than 10 percent of fetuses,
and when no accelerations occur, acidosis is present in
about 50 percent of fetuses

22. Fetal scalp blood sampling
Fetal blood sampling is typically performed using a kit
pH: A scalp pH value of <7.20 has traditionally been used to
represent the critical value for identifying fetal acidosis
 It is no longer used in many institutions , although its use
can result in fewer cesarean deliveries performed for the
indication of nonreassuring fetal status
Fetal lactate concentration
 We do not measure fetal lactate concentrations routinely
because of the practical difficulties of obtaining results,
which are similar to the difficulties of getting results of
fetal pH measurements

23. Fetal pulse oximetry
 There is no evidence that fetal pulse oximetry (FPO)
as an adjunct to electronic FHR monitoring improves
neonatal outcome.
 We do not recommend use of this device because there
is insufficient evidence of any benefit

24. Management of nonreassuring FHR
patterns
 Determine the likely cause of the abnormality, if possible
(eg, abruptio placenta, cord prolapse, maternal medication
, rapid descent of fetal head).
 Attempt to correct the problem or initiate general
measures to improve fetal oxygenation
 Administer oxygen (8 to 10 L/min) to improve fetal
oxygenation. Fetal pO2 and oxygen saturation can reach a
higher steady state within 8 to 10 minutes, but decrease
after supplemental maternal oxygen is withdrawn
 Give an intravenous fluid bolus of nonglucose crystalloid
(eg, 1000 mL)
 Correct hypotension related to neuraxial anesthesia

25.  Discontinue or reduce oxytocin or other uterotonic
agent.
 Iatrogenic tachysystole is a leading cause of
nonreassuring FHR tracings and can be treated
successfully with a beta-adrenergic drug
 Amnioinfusion can be useful in resolving persistent
variable decelerations
 If the nonreassuring pattern does not improve within a
few minutes, perform ancillary tests to determine the
fetal condition.
 Determine whether operative intervention (cesarean
or instrumental vaginal delivery) is needed, and the
urgency of this intervention.

26. SUMMARY AND
RECOMMENDATIONS
 The rationale for monitoring the FHR during labor is that the
fetal response to blood volume changes, acidemia, and
hypoxemia may be reflected indirectly by FHR patterns
 Two commonly used modalities for intrapartum FHR
monitoring are continuous electronic FHR monitoring and
intermittent auscultation
 In uncomplicated pregnancies, there is no evidence that one of
these techniques is better than the other or that use of these
techniques reduces the incidence of stillbirth, low Apgar scores,
neonatal intensive care unit admission, neurological injury, or
cerebral palsy.
 There is evidence that continuous electronic FHR monitoring
leads to higher operative delivery rates than auscultation

27.  For high-risk pregnant women, we suggest continuous rather
than intermittent intrapartum FHR monitoring (Grade 2C).
 For low risk women, we suggest either intermittent or
continuous electronic FHR monitoring (Grade 2C).
 The three tier approach is a useful method for evaluation and
management of FHR patterns
 Transient episodes of hypoxemia, such as during a contraction or
temporary cord compression, are generally well-tolerated by the
fetus
 Repeated or prolonged episodes, especially if severe, may lead to
fetal acidosis
 Further evaluation of a nonreassuring FHR tracing is indicated
to distinguish the fetus who is not hypoxemic, or hypoxemic but
well compensated, from one who is acidotic.
 We recommend assessing the FHR response to stimulation. In
contrast to other modalities, this test is readily available, easy to
perform, inexpensive, and comfortable for the patient.

28.  Normal FHR variability is strongly associated (98 percent)
with an umbilical pH >7.15.
 The combination of undetectable or minimal FHR
variability and late or variable decelerations with late
recovery are the FHR patterns most predictive of acidemia,
although only about 23 percent of fetuses with these
findings will be acidotic.
 If possible, determine the cause of the nonreassuring FHR
and initiate potentially corrective interventions (eg,
discontinuing uterotonic drugs, maternal position change,
IV fluids, oxygen).
 We recommend expeditious delivery for persistent
nonreassuring FHR patterns associated with acidosis or if
the presence of acidosis cannot be excluded (Grade 1C).

29. Thank you