OB Chapter 18 - Fetal Assessment During Labor

categorizing fetal heart rate tracing

- NICHD workshop 2008 proposed a three-tier system for interpretation - category I, Category II, category III

category III

- abnormal and require immediate evaluation and prompt intervention - Nonreassuring FHR patterns associated with fetal hypoxemia - Hypoxemia can deteriorate to severe fetal hypoxia - Absence of baseline variability - Recurrent of late decelerations or varibale decelerations - Bradycardia - Sinusoidal pattern

clinical significance of late decleration

- abnormal pattern associated with fetal hypoxemia, acidemia, and low Apgar scores - considered ominous if persistent and uncorrected, especially when associated with absent or minimal baseline variability

four categories of variability

- absent - minimal - moderate - marked

increase in sympathetic response

- accelerate FHR

before 32 weeks gestation

- acceleration is a peak of 10 beats/minute or more above baseline and duration of at least 10 seconds - acceleration more than 10 minutes is considered change in baseline

nurses role

- acting as partner - teaching and supporting woman and family with understanding labor and birthing process - breathing techniques - use of equipment - pain management techniques - assist with two factors of fetal status: positioning and pushing

amniotomy

- artificial rupture of membrane risk: - increase risk of infection - fetus can compress umbilical cord because looses cushioning/ protection

IA and uterine activity

- assessed by palpation: fingers over fundus before, during, and after contraction - contraction intensity: mild, moderate, or strong - duration: measured in seconds from beginning to end of contraction - frequency: measured in minutes, from beginning of one contraction to beginning of the next - resting tone: between contractions is usually describes as soft or hard

baseline fetal heart rate

- average rate during 10-minute the excludes periodic or episodic changes, periods of marked variability, and segments of baseline that differ by more than 25 beats/min - must be at least 10 minutes of interpretable data in 10 minute segment to determine baseline -normal range: 110-160 beats/minute - preterm fetus baseline is slightly higher

factors evaluated to determine if FHR is normal or abnormal

- based on presence of other obstetric complications progress in labor - use of analgesia or anesthesia - estimated time interval until birth

tachycardia

- baseline FHR greater than 160 beats/minute for 10 minutes or longer - early sign of fetal hypoxemia, especially when associated with late deceleration and minimal or absent variability

bradycardia

- baseline FHR of fewer than 110 beats/minutes for 10 minutes or long - occurs rarely and not specifically related to fetal oxygen - clinical significance depends on underlying cause and accompanying FHR patterns: variability and presence of accelerations or decelerations

five essential components of FHR tracing must be evaluated regularly

- baseline rate - baseline variability - accelerations - decelerations - changed or trends over time

Montevideo units (MVUs)

- calculated by subtracting baseline uterine pressure from peak contraction pressure for each contraction that occurs in 10 minute window - then add together pressures generated by each contraction that occurs during period of time - spontaneous lab begins with MVUs are between 80 and 120 - UA during normal labor rarely exceeds 250 MVUs

decelerations

- caused by dominance of parasympathetic response - may be benign or abnormal - categorized as : early, late, variable, or prolonged - described by visual relation to onset and end of contraction and by their shape

hypotension

- caused by supine maternal posisiton, hemorrhage, or anesthesia

cord blood values suggested in

- cesarean birth for fetal compromise - low 5-minute Apgar score - severe intrauterine growth restriction - abnormal FHR tracing - maternal thyroid disease - intrapartum fever - multifetal gestation

nursing interventions for late deceleration

- change maternal position (lateral) - correct maternal hypotension by elevating legs - increase rate of maintenance IV solution - palpate uterus to assess for tachysystole - discontinue oxytocin if infusing - administer oxygen at 8-10 L/minute by nonrebreather face mask - notify physician - consider internal monitoring for more accurate fetal and uterine assessment - assist with birth if pattern can't be corrected

nursing interventions of variable deceleration

- change maternal position (side to side, knee-chest) - discontinue oxytocin if infusing - administer oxygen at 8-10 L/minute by nonrebreather face mask - notify physician - assist with vaginal or speculum examination to asses for cord prolapse - assist with amnioinfusion if ordered - assist with birth if pattern can't be corrected

hypertension

- chronic hypertension, preeclampsia, or gestational hypertension

absent or miminal variablity

- classified as either abnormal or indeterminate - can result from fetal hypoxemia and metabolic acidemia

documentation

- clear and complete documentation in women's medical record - each FHR and UA assessment should be documented - observations noted and interventions implemented recorded

possible causes of minimal variability

- congenital abnormalities and preexisting neurologic injuries - CNS depressant medications : analgesics, narcotics, barbiturates, tranquilizers, phenothiazens, and general anesthetics

moderate variability

- considered normal - presence is highly predictive of normal fetal acid-base balance - indicates FHR regulations is not significantly affected by fetal sleep cycles (can last 20 minutes), tachycardia, prematurity, congenital anomalies, preexisting neurologic injury, or CNS depressant medication

if abnormal

- corrective measure must be taken to improve fetal oxygenation - intrauterine resuscitation

While evaluating an external monitor tracing of a woman in active labor whose labor is being induced, the nurse notes that the fetal heart rate (FHR) begins to decelerate at the onset of several contractions and returns to baseline before each contraction ends. The nurse should:

- document findings: within normal limits

causes of bradycardia

- fetal cardiac problems: structural defects/ atrioventricular dissociation - viral infections - medications - fetal heart failure - maternal hypoglycemia - maternal hypothermia

MVUs

- first stage 100-250 - second stage: 300-400

relaxation time

- first stage: 60 seconds or more - second stage: 45 seconds or more

fetal compromise

- goals of intrapartum FHR monitoring are to identify and differentiate normal (reassuring) patterns from abnormal (nonreassuring) patterns, which can be indicative of fetal compromise

category II

- indeterminate, includes all tracings that do not meet category I or III criteria - require continued observation and evaluation - make sure mom is in optimal position with oxygen - Bradycardia not accompanied by absence of baseline variability - Tachycardia - Minimal or absence of baseline variability not accompanied by recurrent decelerations - Marked baseline variability - No accelerations in response to fetal stimulation - Periodic or episodic decelerations

amnioninfusion

- infusion of room-temperature isotonic fluid into uterine cavity if volume of amniotic fluid is low - relieves intermittent umbilical cord compression that results in variable deceleration and transient fetal hypoxemia by restoring amniotic fluid volume to normal or near normal levels

monitoring techniques

- intermittent auscultation - external fetal monitoring

What controls FHR?

- intrinsic rhythmicity of fetal heart - central nervous system (CNS) - fetal autonomic nervous system

negative side to IUPC

- invasive - can cause infection - laceration on fetal scalp can occur

variability

- irregular or fluctuations in baseline FHR of two cycles per minute or greater - characteristic of baseline - beats/ minute - measured from peak to trough of single cycle

intermittent auscultation (IA)

- listening to fetal heart rate sounds at periodic intervals to assess FHR - performed with pinard fetoscope, Doppler ultrasound, ultrasound stethoscope, DeLee-Hillis fetoscope - easy to use, inexpensive, and less invasive then EFM, flexibility - used during the beginning of labor - difficult to perform in obese women - used to assess baseline FHR, rhythm, and increases and decreases from baseline

tachycardia results from:

- maternal or fetal infection - maternal fever - fetal cardiac arrhythmias - parasympatholytic drugs (atropine, hydroxyzine) - beta- sympathomimetric drugs ( terbutaline) - maternal hyperthyroidism - drugs (caffeine, cocaine)

tocotransducer/ tocodynamometer

- measures UA transadominally - placed over fundus, held in place by electric belt - measures and records frequency and approximate duration of UCs but not their intensity

conditions needed to use IUPC

- membranes must be ruptures - cervix dilated (2-3 cm) - presenting part low enough to allow placement of spiral electrode or IUPC or both

internal mode:

- more accurate, measures true strength of contraction - measures frequency, duration, and intensity of UC and uterine resting tone - uses spiral electrode: applied to fetal presenting part to assess the FHR and intrauterine pressure catheter (IUPC) to assess UA and uterine resting tone - not interrupted by fetal or maternal movement of affected by maternal size

category I

- normal and strongly predictive of normal fetal acid-base status at time of observation - followed in routine manner and do not require specific action - Baseline FHR in the normal range of 110-160 beats/min - Baseline fetal heart rate variability: moderate - Late or variable decelerations: absent - Early decelerations: may be present or absent - Accelerations: either present or absent

early deceleration clinical signficance

- normal pattern - not associated with fetal hypoxemia, acidemia, or low Apgar scores

clinical significance of acceleration

- normal pattern - signifies fetal well being - represents fetal alertness or arousal states

fetal blood sampling

- obtained through dilated cervix after membranes have ruptured

clinical significance of variable decerlation

- occur in approximately 50% of all labors - usually transient and correctable

balanced increase of sympathetic and parasympathetic

- occurs during contraction, with no observable changes in baseline FHR

Electronic Fetal Monitoring

- ongoing assessment of fetal oxygenation - analyzed for characteristic patterns that suggest fetal hypoxia events and metabolic acidosis during labor two modes: - external mode - internal mode

changes in FHR from baseline

- periodic - episodic

basic corrective measures

- providing oxygen - instituting maternal position changes - increasing intravenous fluid administration

strength

- range from peaking at 40-70 mm Hg in first stage of labor to more then 80 mm Hg during second stage - mild: peak at less than 50 measure internally - moderate: peak at greater then 50

frequency

- ranges from 5-10 per 10 minutes of labor - lower frequencies seen in first stage or labor - high frequencies during second stage of labor

decrease in fetal oxygen supply

- reduction in blood flow through maternal vessels as result of maternal hypertension, hypotension, or hyopvolemia - reduction in oxygen content in maternal blood as result of hemorrhage or severe anemia - alterations in fetal circulation, occuring with compression of umbilical cord - reduction in blood flow to intervillous space in placenta secondary to uterine hyertonus or secondary to deterioration of placenta vasculature assocociated with post-term gestation or maternal disorders (hypertension or diabetes mellitus)

ultrasound tranducer

- reflects high-frequency sound waves off a moving interface (fetal heart and valves) - maternal obesity, occiput posterior position of the fetus, and anterior attachement of the placenta can cause weak or absent signals

sinusoidal pattern

- regular smooth, undulating wavelike pattern - occurs with severe fetal anemia - associated with chorioamnionitis, fetal sepsis, administration of narcotic analgesics

tocolyis

- relaxation of uterus - achieved by administering drugs that inhibit UCs - improves blood flow through placenta by inhibiting UCs - used with other interventions - administered when having excessive spontaneous UCs - used after cesarean birth decided while preparing for surgery - slows down labor - when fetal is in distress

umbilical cord blood acid-base determination

- sample of cord blood useful adjunct to Apgar score - blood withdrawn from both umbilical artery and umbilical vein - tested for pH, carbon dioxide pressure (Pco2), oxygen pressure (Po2 and base deficit or base excess

fetal scalp stimulation and vibroacoustic stimulation

- scalp stimulation: digital pressure during vaginal examination - vibroacoustic stimulation: artificial larynx or fetal acoustic stimulation device on maternal abdomen over fetal head - desired result: acceleration in FHR of at least 15 beats/minute for at least 15 seconds - acceleration indicated absence of metabolic acidemia

Causes of acceleration

- spontaneous fetal movement - vaginal examination - electrode application - fetal scalp stimulation - fetal reaction to external sounds - breech presentation - occiput posterior position - uterine contractions - fundal pressure - abdominal palpation

minimal variability can occur with:

- tachycardia - prematurity - fetus is in temporarily sleep state (do not last longer than 30 minutes)

episodic changes

- those not associated with UCs

periodic

- those that occur with UCs

asphyxia

- used when fetal hypoxia results in metabolic acidosis

Monica AN24

- uses abdominally obtained electronic impulses to monitor FHR and UA - uses five electrode placed on woman's abdomen - transmitted via bluetooth - more accurately measures frequency, peak and duration of UC

causes of oligohydramnios or anhydramnios

- uteroplacental insufficiency - premature rupture of membranes - anomalies that prevent or reduce fetal urine production

variable decelerations

- visually abrupt decrease in FHR below baseline - decrease of at least 15 beats/minute or more below baseline, lasts 15 seconds, and returns to baseline in less than 2 minutes - have U, V, or W shape, characterized by rapid descent and ascent to and from nadir of deceleration - some followed by brief accelerations: shoulders which is compensatory response to compression of umbilical vein

acclerations

- visually apparent abrupt (onset to peak less than 20 seconds) increase in FHR above baseline rate - peak is 15 beats/ minute above baseline, and lasts 15 seconds or more, with return to baseline within 2 minutes - can be periodic or episodic - presence is high predictive of normal fetal acid-base balance- healthy movement

prolonged deceleration

- visually apparent decrease in FHR of at least 15 beats/ minute below baseline and lasting more than 2 minutes but less than 10 minutes - deceleration lasting more than 10 minutes is a change in baseline

late deceleration

- visually apparent gradual decrease in and return to baseline FHR associated with UCs - begins after contraction has started and nadir of deceleration occurs after peak of contraction* - doesn't return to baseline until after contraction is over - attributed to uteroplacental insufficiency - be concerned when have poor variability with late deceleration

early deceleration

- visually apparent gradual decrease in and return to baseline associated with UCs - the onset, nadir (lowest point), and recovery of deceleration correspond to the beginning, peak and end of contraction - "mirror image" of contraction

candidates for amnioinfusion

- woman with abnormally small amount of amniotic fluid (oligohydramnios) - no amniotic fluid (anhydramnios)

resting tone

-average is 10 mm Hg - restores blood flow

increase in parasympathetic response

-produces slowing of FHR

other methods of assessment and intervention

Assessments: - fetal scalp stimulation and vibroacoustic stimulation - umbilical cord acid-base determination - fetal scalp blood sampling Interventions: - amnioinfusion - tocolytic therapy

abnormal patterns

associated with fetal hypoxemia - deficiency of oxygen in arterial blood - if uncorrected, lead to hypoxia: inadequate supply of oxygen at cellular level that can cause metabolic acidosis

woman should

avoid supine position and encourage to maintain side-lying position of semi- Fowler position with lateral tilt to uterus

late deceleration causes

disruption of oxygen transfer from environment to fetus caused by: - uterine tachysystole (more than five contractions in 10 minutes averagered over 30 minute window) - maternal supine hypotension - epidural or spinal anesthesia- (hypotension) - placenta previa - placenta abruption - hypertensive disorders - postmaturity - intrauterine growth restriction - diabetes mellitus - intraamniotic infection

early deceleration causes

head compression resulting from: - uterine contractions - vaginal examination - fundal pressure - placement of internal mode of monitoring

prolonged deceleration causes:

mechanisms responsible for late or variable declarations last for extended period - maternal hypotension - uterine tachysystole or rupture - extreme placental insufficiency - prolonged cord compression or prolapse

terbutaline

most common type of tocolytic - works quickly - improve Apgar scores and cord pH values without apparent complications

fetal response:

oxygen must be maintained to prevent fetal compromise

displayed

paper or computer screen - FHR on upper section - UA in lower section

uterine activity characteristics

provides information on uterine contractions - frequency - duration - strength - resting tone - relaxation - montevideo units (MVUs)

variable deceleration causes:

umbilical cord compression caused by: - maternal position of cord between fetus and maternal pelvis - cord around fetal neck, arm, leg, or other body part - short cord - knot in cord - prolapsed cord

external mode

uses external transducers placed on maternal abdomen to asses FHR and UA - woman in semi-Fowler or later positon - confines woman to bed - ultasound transducer - tocotransducer - Monica AN24

hypovolemia

- hemorrhage

duration

- stable throughout first and second stages - ranging from 45-80 seconds