Fetal Heart Rate

• ·Uterine contractions.
• ·Baseline fetal heart rate.
• ·Baseline FHR variability.
• ·Presence of accelerations.
• ·Periodic or episodic decelerations.
• Changes or trends of FHR patterns over time

• Baseline
• Variability
• Accelerations
• Decelerations
• Uterine Contractions

• average over 10 minute
• rounded to nearest 5 bpm
• normal= 110-160 bpm

picket fences

• >2 bpm, represents intact fetal CNS,
• indicator of well being

w/o medications, previously reassuring tracing w moderate variability changing to minimal variability = an early sign of fetal acidosis, especially when associated with tachycardia and decelerations

• Absent = undetectible
• Minimum = >non detect < 5
• Moderate (reassuring) = 6-25
• Marked= > 25

• Medication or drug response,
• CNS depressants,morphine, demerol, nubain, stadol, nembutal, alcohol, methadone

• fetal sleep cycles
• fetal CNS anomalies, e.g.: anencephaly/hydrocephaly,
• fetal stroke
• prolonged or severe fetal hypoxiacardiac anomalies
• persistent fetal tachycardia
• excessive/prolonged parasympathetic (vagal) stimulation

• Periodic=associated w. contractions
• Episodic= N.A. w. contractions (in between contractions)

• healthy fetus moves, its heart rate accelerates
• quiet sleep state, the fetal heart rate variability is reduced

• episodic or periodic
• adrupt (onset-peak < 30s
• >15 bpm
• >15sec, <2m
• no nursing action

• Presence implies healthy fetus
• moves its HR responds to
• that movement

reassuring findings

• EARLY: periodic, gradual >=30s<2m, tracks w. contraction onset/peak/end, fetal head comp, no nurse action
• 

• LATE: periodic, gradual>=30s<2m, delayed from contraction onset/peak/end, uteroplacenta insufficiency/fetal hypoxia, reqires intervention
• 

• VARIABLE: usually periodic, abdrupt < 15s, >=15 bpm, >30s<2m, cord compression, intervention reqd.
• 

• PROLONGED: adrupt or gradual, usually periodic>15bpm, >2m<10m, prolapsed cord, tachysistol.
• 

FHR response to forces generated by the cervix onto fetal head during uterine contraction

As uterus contracts, fetal head is pressed against cervix...increase CSF pressure

Fetal parasympathetic system activated generates reflex slowing of FHR

Must look at rest of FHR tracing…

• *Deceleration must occur simultaneously w/uterine contraction
• *HR baseline must be in normal range
• *Variability must be moderate early decelerations are normal

allow labor to continue w/o interventions

Ominous finding

HR response to hypoxemia from fetus already experiencing reduced O2 reserves

a reflex slowing of HR in response to drop O2 and fetal BP

True late deceleration accompanied by decrease in variability

Uterine contractionis the stress that bringsout HR response

§ Uterine arteries carry maternaloxygenated blood toplacenta & must pass thru uterine wall

§ During a contraction, the musclefibers of the uterus squeeze downon these vessels & for a few seconds during each contractions, block the blood flow

§ Healthy fetus tolerates brief period w/o fresh O2

§ compromised fetus, whose O2reserves are already reduced, cannot tolerate this brief period w/o O2

• Why the drop in HR?
• *In compromised fetus, the decrease O2 stimulates its chemoreceptors& increases BP
• Both these events stimulate fetal parasympathetic system to slow HR

In severe cases, fetal heart not responding to brain signals =fetus is dying

Most frequent deceleration

• occur anytime umbilical cord is compressed
• Umbilical contains:
• o 1 large, thin-walled umbilical vein
• § Carries oxygenated blood from placenta to fetus

• o 2 thick-walled, smaller arteries
• § Carriesunoxygenated blood fromfetus back to placenta

• When umbilical cord compressed, the 1st affected is large vein
• o Reduces blood flow returning to fetal heart therby decreasing CO
• o Fetus response by brief tachycardia, called “anterior shoulder of variable deceleration”
• o As further pressure is applied toumbilical cord, arteries then becomecompressed
• § Since umbilical arteries come offof the lower aorta, pressure on them increases fetal BP causing reflexive HR, as parasympathetic system is activated

• o When pressure on umbilical arteries is relieved, HR is returned to baseline & may accelerate briefly, called “posterior shoulder”
• o first intervention, along w/providing O2 by face mask, is to change patient’s position to relieve pressure on umbilical cord

baseline >160 bpm for ten minutes between contractions

represents increase in sympathetic and/or decrease in parasympathetic

• fever/infection
• dehydration
• hyperthyroidism
• anemia
• maternal anxiety
• cigarette smoking

• medication parasympatholytic drugs, beta-sympathomimetic drugs,
• illicit drugs
• endogenous adrenaline/anxiety

• fetal activity/stimulation
• chronic fetal hypoxemia
• compensatory response to transient
• fetal hypoxemia

chorioamnionitis (inflammatory reaction in the amniotic membranes)

• fetal cardiac abnormalities
• supraventricular tachycardia
• fetal anemia

baseline rate < 110 bpm for at least ten minutes between contractions

distinguish from the maternal heart rate

• likely a persistent increase
• in parasympathetic (vagal) tone

FHR variability remains moderate with baseline bradycardia, considered benign, tracing reassuring

• maternal supine positioning
• maternal hypotension
• connective tissue diseases
• prolonged maternal hypoglycemia
• maternal hypothermia

medication or drug response, e.g.: inderal, atenolol, labetolol

• umbilical cord occlusion/prolapse
• decompensating fetus
• cardiac conduction defects
• cardiac anatomic defects
• congenital heart disease

• maturity of the parasympathetic nervous
• system

excessive/prolonged parasympathetic (vagal) stimulation

healthy fetus moves, its heart rate accelerates

quiet sleep state, the fetal heart rate variability is reduced

FHR corresponded to UC

·Normal: <5 in 10 minutes, averaged over a 30-minute window.

·Tachysystole: >5 in 10 minutes, averaged over a 30-minute window.

• Characteristics of a uterine contraction:
• o Tachysystole qualified w. presence/absence of FHR decelerations.

tachysystole applies to either spontaneous or stimulated labor.

assessed by palpation or via electronic fetal monitoring (EFM).

Frequency: time from the start of contraction to the start of the next.

Duration: start to resolution

• external tocotransducer applied to abdomen
• *only frequency and duration, not strength

ultrasound device to assess FHR.

accurately assess intensity.

• Measure:
• peak-resting tone
• 1st stage 25-50 mm hg
• 2nd stage 80mm hg
• Mild<50
• Moderate>50
• Resting = 10mm = soft
• ave. during contraction 50-85

Rupture of membranes/cervical dilation are required.

is invasive.


Risk infection/uterine perforation increased.

attention to technique, especially zeroing and calibrating

• catheter tip may become wedged
• preventing production of pressure curve
• *producing distorted, damped, or truncated pressure wave.

meconium or blood may obstruct the catheter.

contraindicated with infections/conditions/sign if bleeding

readings lower Than obtained with sensor-tipped (or solid) catheter.

Catagories I/II/III

– Normal Fetal Acid-Base Status

• o
• Predictable tracings

o Baseline 110 - 160 bpm

o Variability – Moderate

o No late or Variable Decelerations

o Early Decelerations may be seen

• o Accelerations may be present that
• are not necessary

• o Routine Management w/o
• interventions

• – Not Predictive of Acid-Base
• Status

• o
• Considered intermediate tracings

• o Appear frequently & not
• predictive

• o Baseline Tachycardia or
• Bradycardia w/ Minimal or Moderate Variability

• o Min/Absent Variability w/o
• Late/Variable Decelerations

o Marked Variability

o Uncertain response to stimulation

1. Scalp stimulation

2. Vibroacoustic stimulation

• 3. Other fetal stimulation may be
• absent

• o Repetitive Decels w/ Minimal or
• Moderate Variability

• o Prolonged Deceleration ( >
• 2 but < 10 Minutes)

• o Late Decels w/ Moderate
• Variability

• o Variable Decels w/ Slow Return to
• Baseline

• Patients require close
• surveillance &continued re-evaluation

– Abnormal Fetal Acid-Base Status

o Most ominous tracings

o Variability – Absent

• o Recurrent late or Variable
• Decelerations (bradycardia)

• · As an alternative, they may
• experience a Sinusoidal HR

• o Interventions are needed to
• resolve category 3 HR patterns:

1. Administer O2 to mother

2. Change maternal position

3. Stop labor stimulants

• 4. Correct other health issues
• (maternal HYPOtension)

• 5. Expedient delivery, if other
• interventions fail