Fetal Heart Tones and Monitoring MC Exam 2 Blueprint

MC Exam 2

Fetal Reserves

a healthy maternal-fetal placental unit, there is oxygen and nutrients available to the fetus beyond baseline needs of the fetus.

When O2 is decreased, blood flow is deferred to fetal vital organs, then adaptation to labor may begin to be affected

Prolonged or repeated fetal hypoxemia leads to decompensation

Non-Hypoxic fetal reflex

FHR accelerations

Compensatory response to hypoxemia

variable decelerations

Impending decompensation responses

late decelerations

Normal FHR

(110-160) with moderate variability and uterine contractions

Baseline is recorded over a 10-minute period

Absent FHR variability Definition

abnormal finding

No detectable amplitude range to unaided ey

Undetectable variations (0-2 (3) bpm)

Absent FHR Variability Causes

• Fetal sleep cycles

• Fetal tachycardia

• Extreme prematurity

• CNS depressing medications

• Congenital anomalies

• Neurologic injury

• Interruption of fetal oxygenation

Minimal FHR Variability

Abnormal Finding

• Amplitude range ≤ 5 beats/minute

• Visible to unaided eye

similar causes to absent

Moderate FHR variability

Normal Finding - indicates normal FHR regulation and no significant oxygen issues

Peak to trough amplitude is 6-25 bpms  

Marked FHR Variability

• Greater amplitude range

• Often represents normal variant

• Clinical significance not fully known

Abnormal Variability Nursing Interventions

• Change maternal position to side-lying

• Reduce vena cava and aortic compression

• Increase supplemental oxygen

• Increase IV fluid administration

• Monitor response to interventions

Sinusoidal Pattern

• Regular, smooth, undulating wavelike pattern

• Must persist ≥ 20 minutes

• Associated with:

  • Severe fetal anemia

  • Chorioamnionitis

  • Fetal sepsis

  • Opioid medication effects

  • Placental Abruption

FHR Acceleration

Increase in FHR over baseline for greater or equal to 15 seconds (15x15), but equal to or less than 2 minutes.

Before 32 weeks gestation, FHR acceleration definition is equal or greater than 10 bpm over baseline for equal or greater than 10 seconds (10x10).

• Indicates adequate fetal oxygenation

• Highly predictive of normal fetal acid-base balance

• Reassuring sign of fetal well-being

Prolonged Acceleration

acceleration greater than or equal to 2 minutes but less than 10 minutes

Early Decelerations

decrease of FHR below baseline in relation to UC’s: not a bad sign

Nadir (lowest point) of deceleration occurs at the same time as the peak of the UC.

They are a mirror image of one another.

Recovery of FHR baseline is immediate when UC is done.

Early Deceleration Causes

Fetal head compression during UC

Can be sign of baby dropping

Variable decelerations

abrupt decrease of FHR below baseline greater or equal to 15 bpm, lasting equal or more than 15 seconds, but less than 2 minutes

variable shapes and sizes - may be shaped as V’s or U’s 

occurs before, during or after UC’s,

Late Decelerations

Nadir (lowest point of FHR) occurs after peak of UC

slow return to baseline when UC is already done

Late Deceleration Causes

Uteroplacental insufficiency

Late Deceleration Interventions

Reposition mom, give mom fluid bolus, figure out contraction frequency, if on petocin slow or stop, give oxygen later if needed

Prolonged Deceleration

abrupt decrease in FHR baseline that is greater or equal to 15 bpm, lasting more than 2 minutes, but less than 10 minutes

• Extended interruption of fetal oxygen supply

• Mechanisms similar to late/variable decelerations but longer duration

• Can lead to fetal metabolic acidemia if sustained

Normal Contraction Frequency

No more than 5 contractions in a 10 minute period

Category 1 FHR

baseline is 110-160, variability moderate, early decels absent or present, accelerations absent or present

Category 2 FHR 

= equivocal—not 1 or 3—yet… they include any of the following: bradycardia, with absent variability, minimal baseline variability, absent baseline variability not accompanied by recurrent decelerations, marked baseline variability, absence of induced accelerations after fetal stimulation, recurrent variables with minimal or moderate variability, prolonged decelerations greater than 2 minutes, but less than 10 minutes, recurrent late decelerations with moderate variability, variable decelerations with slow return to baseline or overshoots (shoulders)

Category 3 FHR

absent variability with any of the following: recurrent late or variable decelerations, bradycardia, or sinusoidal pattern

VEAL CHOP