electronic fetal monitoring (NST)

1. Non Stress Test
By;
Dr Syeda Sumaiya(2019-
2022)
Pg scholar dept of OBG
NIUM, Bengaluru-91
Under the guidance of;
Prof Wajeeha Begum
HOD dept
of OBG NIUM, Bengaluru-91

2. Freeman (1975) and Lee and colleagues (1975) introduced the nonstress test to
describe fetal heart rate acceleration in response to fetal movement as a sign of fetal
health.
This test involved the use of Doppler-detected fetal heart rate acceleration coincident
with fetal movements perceived by the mother. By the end of the 1970s, the nonstress
test had become the primary method of testing fetal health.
■ Normal Nonstress test
The definition currently recommended by the American College of Obstetricians and
Gynecologists (2016) requires two or more accelerations that peak at 15 bpm or more
above baseline, each lasting 15 seconds or more, and all occurring within 20 minutes
of beginning the test.
It is also recommended that accelerations with or without fetal movements be
accepted, and that a 40-minute or longer tracing—to account for fetal sleep cycles—
should be performed before concluding that there was insufficient fetal reactivity.

3. CONTINUOUS ELECTRONIC FETAL MONITORING (EFM) Indications of
continuous EFM are:
(A) Maternal conditions: Hypertension, previous cesarean delivery, induced labor, APH,
PROM.
(B) Fetal conditions: Small fetus (IUGR), oligohydramnios, multiple pregnancy,
abnormal FHR on auscultation.
Two methods are
applied:
External (From
maternal
abdominal wall –
Noninvasive)
Internal (Directly
from the fetus –
Invasive)

4. Advantages of EFM over clinical monitoring:
Accurate monitoring of uterine contractions.
Significant improvement of perinatal mortality.
Can detect hypoxia early and can explain the mechanism of hypoxia and its specific
treatment.
Improvement of intrapartum fetal death by threefold.
It is an important record for medicolegal purpose.
Drawbacks:
(i) Interpretation is affected by intra- and interobserver error
(ii) Due to error of interpretation, cesarean section rate may be high
(iii) Instruments are expensive and trained personnel are required to interpret a trace
(iv) Mother has to be confined in bed.

6. NATIONAL INSTITUTE OF CHILD
AND HUMAN DEVELOPMENT
(2008), ACOG (2009);
Three tier FHR interpretation system
Category I: Normal (baseline rate 110-160 bpm; FHR variability – moderate; no late
or variable deceleration; early deceleration)
Category II: Indeterminate—all tracings not categorized as category I or III.
Category III: Abnormal (either absent baseline FHR variability and any of the
following: recurrent late/variable decelerations, bradycardia or sinusoidal pattern)

7. Acceleration: Transient increase in FHR by 15 bpm or more lasting for at least 15 seconds.
Prolonged acceleration lasts > 2 min but < 10 min and when it is > 10 min it is a baseline
change. Acceleration denotes an intact neurohormonal and cardiovascular activity and
therefore a healthy fetus.

8. Mechanisms for intrapartum accelerations
Fetal movement
Stimulation by uterine contractions
Umbilical cord occlusion
Fetal stimulation during pelvic examination
Fetal scalp blood sampling
Acoustic stimulation
Finally, accelerations can occur during labor without any apparent stimulus.
Indeed, they are common in labor and are nearly always associated with fetal
movement.

9. Deceleration: Transient decrease in FHR below the baseline by 15 bpm or more and lasting
≥ 15 seconds.
Three basic types of deceleration are observed and are called early, late and variable.

10. Early deceleration (Type I Dips)
Freeman and associates (2003) defined early decelerations as those generally seen in
active labor between 4 and 7 cm dilatation.
In their definition, the degree of deceleration is generally proportional to the
contraction strength and rarely falls below 100 to 110 bpm or 20 to 30 bpm below
baseline.
Such decelerations are common during active labor and not associated with
tachycardia, loss of variability, or other fetal heart rate changes.
Importantly, early decelerations are not associated with fetal hypoxia, acidemia, or
low Apgar scores.
It is due to head compression (vagal nerve activation).

12. Late deceleration (Type II Dips)
A late deceleration is a smooth, gradual, symmetrical decrease in fetal heart rate beginning
at or after the contraction peak and returning to baseline only after the contraction has
ended.
A gradual decrease is defined as 30 seconds or more from the onset of the deceleration to
the nadir. In most cases, the onset, nadir, and recovery of the deceleration occur after the
beginning, peak, and ending of the contraction, respectively.
The magnitude of late decelerations is seldom more than 30 to 40 bpm below baseline and
typically not more than 10 to 20 bpm.
Late decelerations usually are not accompanied by accelerations.. It suggests uteroplacental
insufficiency and fetal hypoxia (50%).
Causes of late deceleration:
(i) Placental pathology (post maturity, hypertension, diabetes, placental abruption)
(ii) Excessive uterine contractions
(iii) Injudicious use of oxytocin
(iv) Regional anesthesia (spinal of epidural).

15. Variable deceleration
Deceleration show abrupt fall in fetal heart rate lasting greater than 15 sec. decelerations vary with
each contractions
The American College of Obstetricians and Gynecologists (2016) has concluded that variable
decelerations, if nonrepetitive and brief—less than 30 seconds— do not indicate fetal compromise
or the need for obstetrical intervention.
In contrast, repetitive variable decelerations— at least three in 20 minutes—even if mild, have been
associated with an increased risk of cesarean delivery for fetal distress.
Decelerations lasting 1 minute or longer have been reported to have an even worse prognosis
(Bourgeois, 1984; Druzin, 1981; Pazos, 1982).

17. Prolonged deceleration
Is the abrupt decrease in FHR to levels below the baseline and it lasts > 2 min but <
10 min. If it lasts > 10 min it is a baseline change.
common causes of Prolonged Deceleration
cervical examination , uterine hyperactivity, cord entanglement, maternal supine
hypotension, Epidural, spinal, or paracervical analgesia, placental abruption, umbilical
cord knots or prolapse, maternal seizures including eclampsia and epilepsy,
application of a fetal scalp electrode, impending birth
Lag period: It is the time taken for the FHR to reach the nadir (the lowest point of the
FHR dip) from the apex of the preceding uterine contraction. In deceleration lag
period is > 30 seconds.

19. Sinusoidal pattern:
It resembles a sine wave. It has a stable
baseline FHR with fixed or absent baseline
variability lasting > 20 min.
Accelerations are absent.
It is often associated with fetal anemia,
fetomaternal hemorrhage, fetal hypoxia
(acidosis).
It may occur when narcotics are given to
mother.
Such FHR patterns are called
pseudosinusoidal as the fetus is well-
oxygenated.

20. Induced fetal stimulation and FHR accelerations: Any FHR acceleration spontaneous
or induced, indicates the absence of fetal acidosis.

21. INTERPRETATION OF A
CARDIOTOCOGRAPHY (CTG)
Accelerations and normal baseline variability (5-25 bpm) denote a healthy fetus.
Absence of accelerations is the first feature to denote onset of hypoxia.
Absence of accelerations, reduced baseline variability of < 5 bpm for > 90 minutes denotes a
hypoxic fetus.
Decreased baseline variability may be due to fetal sleep, infection, hypoxia, anomalies or due
to maternal medications.
Repeated late decelerations increase the risk of low Apgar score and cerebral palsy (CP).
Reduced baseline variability, with late or variable deceleration increases the risk of CP.
Interpretation of the CTG should always be made in the context of clinical picture.

22. REFERENCE
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monitoring (EFM) for fetal assessment during labour. Cochrane Database Syst Rev 2006; 3:CD006066.
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heart rate monitoring: nomenclature, interpretation, and general management principles. Obstet Gynecol 2009;
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Health and Human Development Research Planning Workshop. Am J Obstet Gynecol 1997; 177:1385.
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Y.Spong. Intrapartum assessment In: F.Gary Cunningham, Kenneth J.Leveno, Steven L.Bloom, John C.Hauth,
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