Intrapartum fetal surveillance

week 2/3, chapter 17

Adequate fetal oxygenation depends on five factors:

1. normal maternal blood flow and volume to the placenta

2. normal maternal oxygen saturation

3. adequate placental exchange of oxygen and carbon dioxide

4. an open circulatory pathway between the placenta and fetus through the umbilical cord

5. and normal fetal circulatory and oxygen-carrying function.

Fetal Surveillance

Monitoring the fetus during labor to evaluate fetal well-being and identify changes that may indicate inadequate oxygenation or potential fetal compromise.

Doppler Transducer

An external device that uses ultrasound to detect fetal heart activity and allows the nurse to assess fetal heart tones, baseline rate, rhythm, and changes.

• best to apply in area that corresponds to the fetus back

Electronic Fetal Monitoring (EFM)

A method of continuously monitoring and recording fetal heart rate and uterine activity. Can provide more detailed data and create a permanent record that can be printed or stored electronically.

Ultrasound Transducer

The external EFM device used to detect and record the fetal heart rate.

Tocotransducer (Toco)

An external pressure-sensitive device placed on the maternal abdomen that detects changes in abdominal contour associated with uterine contractions and records uterine activity.

Internal Fetal Monitoring

Fetal monitoring that uses devices placed inside the uterus or attached directly to the fetus. Its main advantage is greater accuracy, but it requires ruptured membranes and approximately 2 cm of cervical dilation and carries a slightly increased infection risk.

Fetal Scalp Electrode (FSE)

An internal fetal monitor attached to the fetal presenting part that detects electrical signals from the fetal heart and provides a highly accurate FHR tracing.

Fetal Scalp Electrode Contraindications/Precautions

The fetal scalp electrode should not be applied to the fetal face, fontanels, or genitals

Intrauterine Pressure Catheter (IUPC)

An internal device placed into the uterus that directly measures uterine activity, including contraction intensity and resting uterine tone.

• measures mercury, the strength of the contractions

External vs. Internal Monitoring

External monitoring is noninvasive but may be less accurate for certain measurements, while internal monitoring provides greater accuracy but requires ruptured membranes and cervical dilation and slightly increases infection risk.

the assessment of uterine contractions uses four components

frequency, duration, intensity, and resting tone.

Contraction Frequency

The number of uterine contractions occurring during a specified period, typically measured from the beginning of one contraction to the beginning of the next.

Contraction Duration

The length of time from the beginning of a uterine contraction until the contraction ends.

Contraction Intensity

The strength of a uterine contraction. With external monitoring, the toco primarily shows the timing and duration of contractions rather than their exact strength; an IUPC can more directly measure contraction pressure.

Resting Tone

The pressure or tension present in the uterus between contractions. With internal monitoring, an IUPC can directly measure resting uterine pressure.

• this should be when the uterus is relaxing and baby is getting oxygen

Normal FHR Baseline

A baseline fetal heart rate of 110–160 beats/minute.

• brady = <110 / 10min

• tachy = > 160 / 10 min

FHR Variability

Fluctuations in the fetal heart rate around the baseline that reflect the interaction between the fetal sympathetic and parasympathetic nervous systems. Variability is an important indicator of fetal neurologic and oxygenation status.

Absent Variability

No detectable variation in the FHR baseline. The amplitude of fluctuations cannot be detected.

Minimal Variability

Detectable FHR fluctuations with an amplitude of ≤5 beats/minute.

Moderate Variability

FHR fluctuations with an amplitude of 6–25 beats/minute. Moderate variability is generally considered reassuring because it indicates an intact fetal autonomic nervous system.

Marked Variability

FHR fluctuations with an amplitude of greater than 25 beats/minute. The tracing has large fluctuations around the baseline and can be difficult to interpret.

Why Is Moderate Variability Important?

Moderate variability is a reassuring finding because it suggests the fetal autonomic nervous system is functioning normally and is associated with adequate fetal oxygenation at that time.

Fetal Sleep and FHR Variability

Fetal sleep can temporarily decrease FHR variability. Reduced variability from sleep may be a normal physiologic finding rather than evidence of fetal compromise.

What factors could influence variability changes

• Narcotics and other sedating medications (Mag sulf.)

• alcohol, drugs

• fetal tachycardia

• gestation less than 28 weeks (less mature)

• fetal anomalies that affect CNS or heart

• hypoxia

what are the periodic changes in fetal heart rate that occur in relation to fetal movement or uterine contractions

accelerations, early decelerations, late decelerations, and variable decelerations.

Acceleration

A visually apparent, abrupt increase in FHR above the baseline. Accelerations are generally reassuring and indicate fetal responsiveness.

• increase in FHR of at least 15 bpm above baseline lasting at least 15 seconds but less than 2 minutes.

Early Deceleration

A gradual decrease in FHR that mirrors the uterine contraction, with the onset and recovery generally corresponding to the beginning, peak, and end of the contraction.

• returns to baseline by end of contraction

Cause of Early Decelerations

Fetal head compression, usually occurring as the fetal head descends during labor.

• generally considered benign/reassuring

Late Deceleration

A gradual decrease in FHR that begins after the uterine contraction reaches its peak and returns to baseline after the contraction ends.

Cause of Late Decelerations

The placenta is not adequately delivering oxygenated blood to the fetus during contractions.

• impaired perfusion exchange/blockade

• not reassuring

Variable Deceleration

An abrupt decrease in FHR that varies in timing, shape, and relationship to uterine contractions. It may have an abrupt onset and recovery.

Cause of Variable Decelerations

Umbilical cord compression, which can temporarily reduce fetal blood flow and oxygen delivery. - need to move cord or mom to relieve pressure

Early vs. Late vs. Variable Decelerations

Early = head compression; late = uteroplacental insufficiency; variable = umbilical cord compression. A useful memory aid is Early = Head, Late = Placenta, Variable = Cord.

FHR Category I

A normal/reassuring fetal heart rate pattern. It includes a baseline of 110–160 bpm, moderate variability, no late or variable decelerations, and may include accelerations and/or early decelerations.

FHR Category II

An indeterminate fetal heart rate pattern that does not meet the criteria for either Category I or Category III. It includes many patterns, such as minimal or marked variability, prolonged decelerations, recurrent variable or late decelerations with certain variability patterns, and other findings requiring continued evaluation.

FHR Category III

An abnormal fetal heart rate pattern associated with a high risk of fetal acidemia when persistent. It includes absent variability with recurrent late decelerations, recurrent variable decelerations, or bradycardia, or a sinusoidal pattern (ongoing, no beat-to-beat)

P.O.I.S.O.N. (A nursing intervention mnemonic for concerning fetal heart rate tracings)

P = Position change (maternal)

O = Oxytocin off

I = IV fluid bolus (500ml of LR over 30min)

S = Sterile vaginal exam

O = Oxygen (10l/min nonrebreather)

N = Notify provider.

VEAL CHOP MINE

• Variable decelerations = Cord compression = Maternal repositioning

• Early decelerations = Head compression = Identify labor progress

• Acceleration = Okay = No interventions

• Late decelerations = Placental insufficiency = Execute interventions

Tachysystole

Excessive uterine activity characterized by more than five contractions in 10 minutes, averaged over a 30-minute window.

• It can reduce the time available for uteroplacental blood flow between contractions and may contribute to fetal oxygenation problems.

Most Reassuring FHR Finding

Moderate variability is one of the most reassuring features of a fetal heart tracing because it indicates an intact fetal autonomic nervous system.

Most Concerning Variability Finding

Absent variability, particularly when accompanied by recurrent late decelerations, recurrent variable decelerations, or bradycardia, is highly concerning and can meet criteria for a Category III tracing.

Late Deceleration Nursing Response

Late decelerations should prompt assessment and interventions aimed at improving fetal oxygenation and uteroplacental perfusion, including the P.O.I.S.O.N. interventions when indicated.