““FETAL HEART MONITORING”FETAL HEART MONITORING”

Dr Seyed Asadollah KalantariDr Seyed Asadollah KalantariOB & GynecologistOB & Gynecologist

Isfahan Fertility & Infertility CenterIsfahan Fertility & Infertility Center

FETAL MONITORINGFETAL MONITORING

• Non Stress Tests

• Contraction Stress Tests

Non stress test

Non stress testNon stress testA nonstress test determines the response of the

fetal heart rate to fetal movements.• “running a strip.” During a nonstress test, an

external monitor is placed around the mother's abdomen to record the fetal heart rate.

• Each time ,the fetal movement is noted on the recording chart.

• If the fetus is asleep, the mother press on her abdomen or make a loud noise to awake the fetus.

Cont OB/GYN 2005;50:38-48

Cont OB/GYN 2005;50:38-48

Non stress testNon stress test

• The NST is derived from observations that a fetus that is not acidotic and has an intact normally functioning autonomic nervous system will have periodic accelerations of the FHR.

Non-stress test physiology• Afferent signals:

– Baroreceptors: aorta, atrium, carotids– Proprioceptors: joints– Pain fibers: skin

• When stimulated, send afferent impulses to brain to increase FHR

• Efferent signals increase FHR

• If movement and accelerations observed, reasonable to conclude the afferent and efferent limbs intact and cardioregulatory neurons adequately oxygenated

Indications for the NST

• Suspected post-maturity• Maternal diabetes• Maternal hypertension: chronic and

pregnancy-related disorders• Suspected or documented IUGR • History of previous stillbirth• Isoimmunization

Indications for the NST

• Older gravida• Decreasing fetal movement • Sever maternal anemia• Multiple gestation• High-risk antepartal conditions: PROM, PTL,

bleeding• Chronic renal diseases

Factors that can interfere with NSTFactors that can interfere with NST• Fetal positions • Being unable to lie still throughout the procedure• Being overweight• An infection in either you or your baby. • Low (hypoglycemia) or high (hyperglycemia) blood

sugar levels. • Medications, such as magnesium sulfate. • Alcohol. • Illegal drugs, such as cocaine. • stool (feces) or air in the intestines or rectum

interfering with the fetal ultrasound

NST: How to do itNST: How to do it• Patient in lateral tilt position• Tracing observed for 40 minutes• Accelerations peak (but do not

necessarily remain) at least 15 BPM above baseline

• Last for 15 seconds• Reactive: 2 or more accelerations

within 20 m period• Nonreactive: one that lacks

sufficient accelerations over 40 minute period

• No contraindications

The preterm fetusThe preterm fetus

• Frequently nonreactive

– 24-28 weeks, up to 50% of NST nonreactive

– 28-32 weeks, 15% nonreactive

Reactive NST (Acceleration)

• Non Reactive NST (Lack of Acceleration )• Fetal sleep • Medication• Hypoxia

Contraction stress test

• (CST) measures the fetus''s ability to tolerate the stress of uterine contractions started (induced) before true labor begins.

• during a contraction stress test ,evaluate the fetus''s heart rate during contractions.

• helps evaluate the placenta''s ability to provide enough oxygen to the fetus.

• For determine the safest method of delivery. • A contraction stress test is also called an

oxytocin challenge test.

• the hormone oxytocin is given to cause labor contractions.

• you may massage your nipples to prompt your body to release oxytocin.

• (decelerates) instead of (accelerates) after a contraction, baby not be able to tolerate the stress of normal labor.

• A contraction stress test is often done if a baby''s heart rate is abnormal during (nonstress test).

• This test may be used in rare cases for women who have had an abnormal nonstress test or biophysical profile

Contraction stress testContraction stress test

CST interpretationCST interpretationInterpreted as to the presence or absence of late

decelerations•Negative: no late or significant variable decelerations•Positive: Late decels following 50% or more of contractions•Equivocal: intermittent late decels or significant variable decels•Equivocal-hyperstimulatory: FHR decels in presence of contractions occurring more than every 2 minutes or lasting longer than 90 seconds•Unsatisfactory: fewer than 3 contractions in ten minutes

Contraction stress test

• Contraindications:–Preterm labor patients at high risk of

preterm labor–PROM–History of extensive uterine surgery or

classical cesarean–Known placenta previa

• Positive contraction stress test• Fetal heart rate decceleration• Fetal hypoxia (uteroplacental insufficiency)

• Negative contraction stress test• Fetal heart rate decceleration

FHR VariabilityFHR Variability

• Increased Variability: marked variability from a previous average variability.

– Causes: -early mild hypoxia - fetal stimulation - uterine palpation - contractions - fetal activity - maternal activity - illicit drugs

• Saltatory ( Increased Variability) pattern with wide variability. The oscillations of the fetal heart rate above and below the baseline exceed 25 bpm.

FHR Variability

• Decreased Variability: marked decrease in variability from a previous average variability.– Causes: hypoxia / acidosis; CNS depressants;

analgesics / narcotics; barbiturates; tranquilizers, anaractics; parasympatholytics; general anesthetics; prematurity (<24 wks); fetal sleep cycles; congenital abnormalities; fetal cardiac dysrhythmias.

FHR VariabilityFHR Variability• Decreased Variability (continued):– Significance: benign when associated with fetal

sleep cycles; if drugs, variability usually increases as drugs are excreted; when associated with uncorrectable late decelerations indicates presence of fetal acidosis and can result in low APGARs.

– Nsg.Interventions: none, if fetal sleep cycle, or CNS depressants; consider fetal scalp stimulation or apply a spiral electrode; monitor fetal oxygen saturation; prepare for birth if indicated.

Selected High-Risk Indications for Continuous Monitoring of Fetal Heart Rate

• Maternal medical illness- Gestational diabetes- Hypertension- Asthma

• Obstetric complications- Multiple gestation- Post-date gestation- Previous cesarean section- Intrauterine growth restriction- Premature rupture of the membranes- Congenital malformations- Third-trimester bleeding- Oxytocin induction/augmentation of labor- Preeclampsia

• Psychosocial risk factors- No prenatal care- Tobacco use and drug abuse

Factors that can interfere with Factors that can interfere with Electronic fetal monitoringElectronic fetal monitoring

• Nicotine or caffeine which can falsely raise your baby's heart rate and produce inaccurate test results.

• Extra noises such as your heartbeat or your stomach rumbling.

• baby is sleeping during a nonstress test. • Fetal movement during the test. If your baby is

moving a lot, it may be difficult to correctly position the external montioring device.

• Being overweight, or pregnant with multiple babies. In these cases it may be difficult to correctly position the external monitoring device.

INDICATIONINDICATION Electronic fetal monitoring Electronic fetal monitoring

• diabetes

• high Blood Pressure

• small baby or baby not growing properly

• past your due date

• too much or too little fluid around the baby

• Baseline fetal heart rate is 130 to 140 beats per minute (bpm), preserved beat-to-beat and long-term variability. Accelerations last for 15 or more seconds above baseline and peak at 15 or more bpm. (Small square=10 seconds; large square=one minute)

Increase the baseline fetal heart• Prematurity• maternal anxiety • fever rate

Decreases the baseline fetal heart• fetal maturity

Periodic FHR Changes

• Accelerations • Early Decelerations• Late Decelerations • Variable Decelerations• Sinusoidal Pattern

Accelerations

• fetal movement. • Partial umbilical cord compression This occurs with normal autonomic

function, which acts to preserve cardiac output by increasing heart rate in response to decreased blood return to the fetal heart.

Decelerations• 50% of NST• Non repetitive and less than 30 seconds in duration,

obstetric intervention is not needed

• repetitive decelerations or decelerations that last longer than 60 seconds are associated with an increased risk of fetal demise and cesarean delivery for the diagnosis of nonreassuring FHR pattern

Early Decelerations

• Definition: a transitory gradual decrease and return to baseline FHR in response to fetal head compression.

• Generally starts before the peak of the uterine contractions.

• Returns to the baseline at the same time as the contraction returns to its baseline.

• Considered benign. No interventions.

• Early deceleration in a patient with an unremarkable course of labor. Notice that the onset and the return of the deceleration coincide with the start and the end of the contraction, giving the characteristic mirror image.

• Late deceleration with loss of variability. This is an ominous pattern, and immediate delivery is indicated.

• Nonreassuring pattern of late decelerations with preserved beat-to-beat variability. Note the onset at the peak of the uterine contractions and the return to baseline after the contraction has ended. The second uterine contraction is associated with a shallow and subtle late deceleration.

Late DecelerationsLate Decelerations• Definition: a transitory gradual decrease in and return to

baseline of FHR associated with contractions.• Begins after the contraction has started, and the lowest

part of the decel occurs after the peak of the contraction.• Usually does NOT return to baseline until after the

contraction is over.• Indicates uteroplacental insufficiency. Interventions

required!• Considered ominous sign when they’re uncorrectable,

especially when associated with decreased variability and tachycardia.

Late DecelerationsLate Decelerations• Interventions:– Change maternal position (lateral)– Correct maternal hypotension (elevate legs)– Increase rate of maintenance IV– D/C oxytocin if infusing– Administer O2 at 8-10 L/min (face mask)– Fetal scalp or acoustic stimulation– Assist with fetal O2 saturation if ordered– Assist with birth if pattern cannot be corrected.

• Late deceleration with loss of variability. This is an ominous pattern, and immediate delivery is indicated.

Late deceleration

Variable DecelerationsVariable Decelerations• Definition: an abrupt decrease in FHR that is

variable in duration, intensity,and timing related to onset of contractions; caused by umbilical cord compression.

• Onset to the beginning of the nadir is <30 seconds; decrease in > 15 bpm, lating >15 seconds; variable times in contracting phase; often preceded by transitory acceleration.

• Return to baseline is rapid and <2 min from onset; sometimes with transitory acceleration immediately before and after decel.

• Described as: mild, moderate, or severe.

Variable DecelerationsVariable Decelerations• Interventions:– Change maternal position (side to side).

• If severe:– D/C oxytocin if infusing– Administer O2 at 8-10 L/min (face mask)– Assist with vag or speculum exam– If cord is prolapsed, examiner will elevate fetal

presenting part with cord between gloved fingers until c/s is accomplished

– Assist with amnioinfusion if ordered– Assist with fetal O2 saturation monitoring if

ordered– Assist with fetal O2 saturation if ordered

• Variable deceleration with pre- and post-accelerations ("shoulders"). Fetal heart rate is 150 to 160 beats per minute, and beat-to-beat variability is preserved.

• Severe variable deceleration with overshoot. However, variability is preserved

Prolonged DecelerationsProlonged Decelerations• Definition: a visually apparent decrease in

FHR below the baseline 15 bpm or more and lasting more than 2 minutes but less than 10 minutes.

• Benign causes: pelvic exam, application of spiral electrode, rapid fetal descent & sustained maternal valsalva maneuver.

• Other causes (severe): progressive severe variable decels, sudden umbilical cord prolapse, hypotension, paracervical anesthesia, tetanic contraction & maternal hypoxia (may occur with seizure).

Signs of Nonreassuring Variable Signs of Nonreassuring Variable Decelerations that Indicate Decelerations that Indicate

HypoxemiaHypoxemia • Increased severity of the deceleration• Late onset and gradual return phase• Loss of "shoulders" on FHR recording• A blunt acceleration or "overshoot" after

severe deceleration• Unexplained tachycardia• Saltatory variability• Late decelerations or late return to

baseline• Decreased variability

InterferenceInterference• Hypoxemia • Acidemia• oligohydramnios interfere with measures of central nervous system (CNS) performance, such as• FHR patterns• Fetal movement• Tone

Other DEFINITIONSOther DEFINITIONS

• Tachycardia: a baseline FHR >160 bpm for a duration of 10 minutes or longer.

• Bradycardia: a baseline FHR <110 bpm for a duration of 10 minutes or longer.

Fetal MonitoringFetal Monitoring

Bradycardia

Fetal heart rate less than 120 bpmIf longer than 5 minutes, consider delivery

Can tolerate 80-90's for about 20 minutesCan tolerate 60-70's for only about 6-10 minutes

Common etiologies:Maternal hypotensionMaternal hypoxiaHypothermiaPlacental abruptionUterine tetany

BradycardiaBradycardia

• Baroreceptors influence the FHR through the vagus nerve in response to change in fetal blood pressure

• Hypoxia• uterine contractions• fetal head compression• fetal grunting

Causes of Severe Fetal BradycardiaCauses of Severe Fetal Bradycardia

• Prolonged cord• compression Cord• prolapse Tetanic• uterine contractions• Paracervical block

Epidural and spinal anesthesia

Maternal seizures Rapid descent Vigorous vaginal

examination

TachycardiaTachycardia

• Chemoreceptors located in the aortic and carotid bodies respond to hypoxia, excess carbon dioxide and acidosis, producing tachycardia and hypertension.

Fetal MonitoringFetal Monitoring

Tachycardia

Fetal heart rate greater than 160 bpmUsually tolerated well

Common etiologies:• maternal fever• chorioamnionitis• Beta-agonists

• Fetal tachycardia with possible onset of decreased variability (right) during the second stage of labor. Fetal heart rate is 170 to 180 bpm. Mild variable decelerations are present.

Fetal MonitoringFetal Monitoring

Sinusoidal PatternSinusoidal Pattern

Fetal heart rate exhibits a sinusoidal wave formCommon etiologies :

• Fetal anemia• Fetal hypoxia• Breech presentation

• True sinusoidal pattern Note the decreased regularity and the preserved beat-to-beat variability,

• Pseudosinusoidal pattern• Note the decreased regularity and the

preserved beat-to-beat variability

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