Chapter 19: Fetal Health Surveillance

Labour is a period of physiological stress for the fetus. fetal oxygen supply is affected by uterine activity

Why is monitoring fetal status an essential part of nursing care throughout labour?

1. Decreased maternal arterial oxygen tension

   1. Respiratory disease

   2. Hypoventilation, seizure, trauma

   3. Smoking

   4. Obesity (BMI > 35 kg/m2)

2. Decreased maternal oxygen-carrying capability

   1. significant anemia (e.g., iron deficiency, hemoglobinopathies)

   2. Carboxyhemoglobin (smokers)

3. Decreased uterine blood flow

   1. Hypotension (e.g., blood loss, sepsis)

   2. Regional anaesthesia

   3. Maternal positioning

4. Chronic maternal conditions

   1. Vasculopathies (e.g., systemic lupus erythematosus, type I diabetes, chronic hypertens

Maternal factors that may affect fetal oxygenation in Labour: [14]

Excessive uterine activity

• Tachysystole secondary to oxytocin, prostaglandins (PGE2), or spontaneous labour

• Placental abruption

Uteroplacental dysfunction

• Placental abruption

• Placental infarction—dysfunction marked by IUGR, oligohydramnios, or abnormal Doppler studies

• Chorioamnionitis

• Uterine rupture

uteroplacental factors that may affect fetal oxygenation in labour: [8]

Malpresentation (e.g., breech)

Polyhydramnios

Oligohydramnios

Cord compression, prolapse or entanglement

• ≥ 3 nuchal loops

Umbilical cord knots

Single umbilical artery

Decreased fetal oxygen carrying capability

• Significant anemia (e.g., isoimmunization, maternal–fetal bleed, ruptured vasa previa)

• Carboxyhemoglobin (if mother is a smoker)

Fetal factors that may affect fetal oxygenation in labour [10]

hourly

How often should FHR be assessed in latent stage? (SOGC)

every 15-30 minutes

How often should FHR be assessed in the active stage? (SOGC)

every 15-30 minutes

How often should FHR be assessed in passive phase of second stage? (SOGC)

every 5-10 minutes, depending on method being used

How often should FHR be assessed in active phase of second stage? (SOGC)

1. before artificial rupture of membranes

2. after artificial rupture of membranes

3. with administration of medications and anesthesia

4. more frequently with atypical or abnormal FHR patterns

Aside from normal checks, when should FHR be assessed? [4]

1. normal

2. atypical

3. abnormal

Three fetal heart rate patterns

normal

fetal heart patterns requiring no interventions

atypical

fetal heart patterns requiring vigilence and ongoing monitoring

Abnormal

fetal heart pattern requires various interventions, potentially including expediting birth

by palpation.

Additionally, can use external tocotransducer or internal intrauterine pressure catheter

How is uterine activity assessed?

internal intrauterine pressure catheter (IUPC)

internal device that measures uterine activity, used in conjunction with EFM

1. frequency

2. duration

3. intensity

4. resting tone

components of assessment of uterine activity: [4]

Measured by determining the number of contractions in a ten minute period, averaged over a 30 minute window

how is contraction frequency measured?

Measured in seconds, from he beginning to the end. Expressed as a range in seconds, from shortest to the longest contraction occured at the time being documented

how is duration of contractions measured?

45-80 seconds

How long do contractions last (range)

90 seconds

Contractions should not last longer than how many seconds?

described as mild, moderate, or strong.

How is intensity of contractions measured by palpation?

measured in mmHg

how is intensity of contractions measured by IUPC?

Uterus is easily indented upon palpation, feels like the tip of the nose

How does a mild contraction feel upon palpation?

Can be slightly indented upon palpation, fees like the chin.

How do moderate contractions feel upon palpation?

Cannot indent upon palpation, feels like the forehead

How do strong contractions feel upon palpation?

resting tone

degree of muscular tension when the uterus is relaxed

palpation: should be described as soft.

IUPC: less than 25mmHg

How is resting tone measured?

As least 30 seconds

How long should time between contractions be?

5 contractions or less occuring in a ten minute window, averaged over a 30 minute time period

Normal uterine activity pattern is how many contractions in a ten minute window?

Tachysystole

Greater than 5 contractions in 10 minutes, averaged over a 30 minute window

by presence or absence of associated FHR changes

How is tachysystole qualified?

It denotes normal intermittent auscultation patterns. monitor required.

Why is tachysystole a reason to put on EFM?

110-160bpm

Normal baseline FHR

Regular (E.g., no skipped beats)

Regular fetal heart rhythm (only heard with IA)

Range of 6-25 bpm

Range of moderate FHR variability

It increases the rate of c-section, interventions, operative vaginal births, and greater use of analgesia and anesthesia

why should only high risk pregnancies be put on EFM?

• Lack of nursing staff to provide one-to-one supportive care

• Caregiver skill and comfort with IA

• False belief that EFM will prevent bad outcomes

• False caregiver belief that EFM records will prevent medical legal actions

Why does EFM se remain so high? [4]

1. pinard stethoscope

2. doppler ultrasound (Doptone)

3. ultrasound stethoscope

4. DeLee-Hillis fetoscope

instruments for intermittent auscultation: [4]

Doptone

Tool used most frequently for IA, transmits ultra-high frequency sound waves reflecting movement of the fetal heart and converts these sounds into an electronic signal that can be counted

Between contractions

When is fetal heart assessed?

Area of maximal intensity, usually the fetal back

Where to listen in IA:

For healthy patients at term who are not expected to experience adverse perinatal outcomes

Who should IA be used for?

To insure that the identified FHR is not in fact a maternal heart rate

Why is it important to palpate maternal pulse during IA?

1. classify findings as normal or abnormal

2. interpret findings in light of the total clinical picture

3. respond on the basis of assessment findings and clinical knowledge.

Why is it important to assess uterine activity with FHR? [3]

1. hypoxia

2. metabolic acidosis

two major fetal complications associated with abnormal FHR

1. external transducers

2. internal spiral electrode

Two modes of EFM:

involves application of a spiral electrode to the fetal presenting part by 1.5mm to assess FHR. Can only be used once membranes have ruptured and cervix is dilated at least 2-3cm

Internal mode of EFM:

Tocotransducer:

Monitors frequency and duration of contractions by means of a pressure-sensing device applied to the maternal abdomen. Cannot measure intensity.

Ultrasound transducer (tocodynamometer)

High-frequency sound waves reflect mechanical action of the fetal heart; noninvasive, does not require rupture of membranes or cervical dilation

1. BMI greater than 35

2. OP position

3. Anterior attached placenta

What can cause weak signals of tocotransducer? [3]

Every hours as the labouring patient and fetus change position

When should the toco monitor be repositioned. Why?

pregnancies at risk for adverse fetal or newborn outcomes, NOT to determine if a patient is in labour

Who should have a 20 minutes monitor strip on admission to measure fetal heart?

• 100-110

• >160 for 30-80 minutes

• arrythmias

atypical baseline fetal heart rate [3]

less than 100

greater than 160 for more than 80 minutes

erratic baseline

Abnormal baseline fetal heart rate [3]

1. moderate variability (6-25 bpm)

2. less than 5bpm for less than 40 minutes

Normal variability in fetal heart [2]

less than or equal to 5 bpm for 40-80 minutes

Atypical variability for fetal heart

1. less than or equal to 5bpm for more than 80 minutes

2. greater than or equal to 25bpm for >10 mintes

3. sinusoidal

abnormal variability for fetal heart

1. spontaneous (present, not required)

2. accelerations with scalp stimulation

Normal accelerations in fetal heart [2]

absence with scalp stimulation

Atypical accelerations in fetal heart

Absence

Abnormal accelerations in fetal heart

1. none

2. nonrepetitive uncomplicated variables

3. early decelerations

Normal decelerations in fetal heart [3]

1. repetitive uncomplicated variables

2. nonrepetitive complicated variables

3. intermittend late decelerations

4. single prolonged deceleration for >2mins but < 3 mins

Atypical decelerations in fetal heart [4]

1. repetitve complicated variables

2. recurrent late decelerations

3. single prolonged deceleration for >3mins but <10 mins

Abnormal decelerations in fetal heart [3]

Normally a physiological response. Monitor closely

Clinical interpretation (in light of whole situation) of atypical fetal heart findings:

possible fetal compromise

Clinical interpretation (in light of whole situation) of abnormal fetal heart findings

Recurrent decelerations

Decelerations that occur with at least 50% of uterine contractions in any 20 minute window

Intermittent decelerations

Decelerations occur with no more than 50% of uterine contractions in any 20 minute segment

Repetitive decelerations

greater than or equal to 3 decelerations in a row

Nonrepetitive decelerations

1 or maximally 2 decelerations in a row

Rounded o increments of 5 beats per minte during a 10 minute tracing segment. Excludes accels, decels, and period of marked variability. Must be present for at least 2 minutes in any 10 minute segment baseline

How is baseline FHR approximated?

Baseline FHR greater than 160 that lasts for more than 10 minutes

fetal tachycardia is defined as:

atypical or abnormal, depending on length of time it occurs

Fetal tachycardia is labelled as what?

Maternal fever

Most common cause of fetal tachycardia:

1. maternal or fetal infection

2. maternal hyperthyroidism

3. fetal anemia

4. maternal administration of medications or illicit drugs

Other causes of fetal tachycardia: [4]

Potential fetal hypoxemia, especially when associated with decreasing variability and decelerations

Fetal tachycardia can be a warning sign for what?

FHR of less than 110 lasting for more than 10 minutes

Fetal braycardia is defined as

1. fetal hypoxia/acidosis

2. AV dossociation

3. structural defects

4. viral infection

5. medications

6. maternal hypotension

7. fetal heart failure

8. maternal hypoglycemia

9. maternal hypothermia

10. maternal position

potential causes of fetal bradycardia [10]

Depends on the underlying cause and accompanying FHR patterns, including variability, and presecne of accels/decels

Clinical significance of fetal bradycardia:

1. decelerations (variable or late decelerations)

2. absent variability

Tachycardia is abnormal when associated with what? [2]

Variability

Refers to fluctuations in the baseline FHR that are irregular in amplitude and frequency and are visually quantified as the amplitude of the peak to trough in bpm.

1. absent

2. minimal

3. moderate

4. marked

classifications of variability: [4]

Marked variability

Amplitude range in variability is greater than 25 bpm

minimal variability

amplitude range is detectable but less than or equal to 5 bpm

Absent variability

variability where amplitude range is undetectable (0-2bpm)

1. fetal hypoxemia

2. metabolic acidemia

Minimal or absent FHR variability can result from what? [2]

1. fetal sleep

2. fetal tachycardia

3. medications

4. prematurity

5. congenital abnormalities

6. fetal anemia

7. cardiac arrhythmias

8. infection

9. pre-existing neurological injury

Other conditions potentially associated with minimal or absent variablity:

if marked variability persists for 10 minutes or more

When does marked variability require urgent action, such as fetal scalp pH or lactate sampling?

Sinusoidal FHR pattern

FHR pattern is a smooth, wavelike undulating pattern with a cycle frequency of 3-5 waves/min that persists for 20 minutes or more.

Periodic changes

Changes in FHR from baseline occur with uterine contractions

Episodic changes

Changes in FHR that are not associated with uterine contractions

Acceleration

Visually apparent, abrupt (onset to peak is less than 30 seconds) increase in FHR above baseline rate.

Peak is at least 15 bpm above baseline, acceleration lasts 15 seconds or longer, with a return to baseline in less than 2 minutes.

How are FHR accelerations defined?

peak is 10 bpm above baseline, duration less than 10 minutes.

How are accelerations described before 32 weeks gestation?

Prolonged acceleration

An acceleration of FHR that lasts longer than 2 minutes but less than 10 minutes

An acceleration that lasts longer than 10 minutes

When is an acceleration considered a change in baseline rate?

1. spontaneous fetal movement

2. fetal stimulation from

   1. vaginal exam

   2. electrode application

   3. fetal scalp stimlation

3. fetal reaction to external sounds

4. uterine activity

5. abdominal palpation

6. fundal pressure

7. brief occlusion of umbilical vein only

Causes of FHR accelerations: [7]

Normal pattern: acceleration with fetal movement signifies well-being, representing fetal alertness or arousal states. No intervention required.

Clinical significance of FHR accelerations:

1. early

2. late

3. variable

4. prolonged

FHR decelerations can be categorized as: [3]

Repetitive decelerations

Deceleration are greater than 3 in a row.

Recurrent decelerations

decelerations if they occur with greater than or equal to 50% of uterine contractions in any 20 minute window.