CJ

Intrapartum Fetal Surveillance

Module 5 Overview

  • Instructor: Kathryn Zeigler, DNP, FNP-C

Chapter 17: Intrapartum Fetal Surveillance

Fetal Oxygenation

  • Requirements for Adequate Fetal Oxygenation:

    • Normal maternal blood flow and volume to the placenta

    • Normal oxygen saturation of maternal blood

    • Normal fetal circulatory and oxygen-carrying functions

    • An open circulatory path between the placenta and fetus through vessels in the umbilical cord

    • Adequate exchange of oxygen and carbon dioxide in the placenta

Maternal Arterial System and Placental Function

  • Components Involved in Fetal Oxygenation:

    • Maternal arterial system

    • Intervillous space where the exchange of O2/CO2 and nutrients/waste occurs

    • Chorionic villi enable nutrient exchange

    • Umbilical vein via spiral arteries connects to the placenta

Fetal Heart Rate (FHR) Regulation

  • Conversion of increased cardiac output in the fetus:

    • Achieved primarily through an increase in heart rate.

    • Conversely, a marked decrease in FHR decreases cardiac output.

  • Influencing Systems:

    • Sympathetic Nervous System:

    • Catecholamines (epinephrine and norepinephrine) increase heart rate and consequently cardiac output.

    • Parasympathetic Nervous System (PNS):

    • Vagus nerve: Reduces FHR and maintains variability; greater influence is seen starting at 28-32 weeks.

    • Autonomic Nervous System Response:

    • Baroreceptors located in major arteries respond to stretching with increased blood pressure.

    • May stimulate the vagus nerve to decrease FHR and BP, leading to decreased cardiac output.

  • **Central Nervous System Components:

    • Cerebral cortex causes FHR to increase with fetal movement and decrease with sleep.

    • Hypothalamus coordinates the two branches of the autonomic nervous system.

    • Medulla oblongata maintains a balance between the two opposing forces that adjust FHR.

  • Adrenal Glands:

    • Secrete epinephrine and norepinephrine in response to sympathetic nervous stimulation.

    • Effects: Increases FHR, decreases BP leading to the release of aldosterone and sodium retention, resulting in increased fetal blood volume.

  • Chemoreceptors:

    • Respond to changes in oxygen, carbon dioxide, and pH.

  • Sighting Locations for Chemoreceptors:

    • Located in the medulla oblongata and at aortic and carotid bodies.

    • Notable role in the response to low O2 by increasing cardiac output.

Pathological Influences on Fetal Oxygenation

  • Factors affecting fetal oxygenation:

    • Alterations in the placenta or issues related to either fetal factors or the mother.

    • Maternal Influences:

    • Hypotension: Decreases perfusion to the placenta.

    • Hypertension: Compromises blood flow.

    • Maternal acid-base alterations: Affect fetal condition.

    • Lower maternal O2 tension: Leads to fetal distress.

  • Uterine Activity:

    • Tachysystole may lead to fetal compromise even with weak uterine contractions.

  • Umbilical Flow Interruptions:

    • Causes:

    • Abruption and infarction of the placenta.

Antepartum and Intrapartum Considerations

Maternal History and Risk Factors for Fetal Compromise

  • Risk Factors:

    • Previous stillbirth (unexplained or possibly recurring causes)

    • Previous cesarean section

    • Poor nutrition, low pre-pregnancy weight, inadequate weight gain

    • Multiple pregnancies with close spacing

    • Presence of chronic diseases (cardiac, anemia, hypertension, diabetes, asthma, autoimmune diseases)

    • Acute infections (urinary tract, pneumonia, gastrointestinal)

    • Hematologic issues (anemia, deep vein thrombosis)

    • Use of drugs (prescription, OTC, herbal, illicit)

    • Psychosocial stressors (domestic violence)

  • Identified Problems During Pregnancy:

    • Intrauterine growth restriction (IUGR)

    • Gestation >42 weeks

    • Marked decrease in fetal movement

    • Multifetal gestation

    • Preeclampsia or eclampsia

    • Gestational diabetes

    • Placental abnormalities (placenta previa, abruptio placentae)

    • Severe maternal anemia

    • Maternal infection and trauma

    • Hypotension or hypertension

    • Hypertonic uterine contractions

    • Abnormal labor (preterm or dysfunctional)

    • Prolonged rupture of membranes

    • Chorioamnionitis

    • Fever

  • Fetal and Placental Problems:

    • Fetal anemia

    • Persistent abnormal or nonreassuring fetal heart rates/patterns

    • Meconium-stained amniotic fluid

    • Abnormal fetal presentation or position

    • Prolapsed cord

    • Abruptio placentae

Intermittent Auscultation and Fetal Heart Rate Assessment

Steps for Procedure: Intermittent Auscultation

  • Preparation Steps:

    • Explain the procedure and perform hand hygiene.

    • Use Leopold maneuvers to identify the fetal back (FHTs usually heard loudest over the fetal back).

  • Assessing FHR:

    • If normal, document findings; if abnormal, apply Continuous Electronic Fetal Monitoring (CEFM).

    • Assess fetal heart rate (FHR) using a Doppler transducer or fetoscope.

    • Verify the heartbeat is fetal by comparing with the mother’s radial pulse rate.

    • Count the baseline for 30-60 seconds between contractions (ctx).

  • Reassuring Findings:

    • FHR of 110-160 bpm

    • Regular rhythm

    • Accelerations present

    • No decelerations

Electronic Fetal Monitoring (EFM) Considerations

  • Benefits and Limitations:

    • Continuous or intermittent:

    • Reduced mobility.

    • Adjustment with position changes may be needed; belts may be uncomfortable.

    • Medicalizes labor; however, provides more data.

    • Offers a permanent record and trends over time and includes ctx information, along with fetal reactions.

    • Baseline Variance Conditions:

    • Baseline: 110-160 bpm

    • Variability: Moderate (6-25 bpm)

    • Accelerations defined as 15 x 15 or (10 x 10 for ≤ 32w)

    • Decelerations: absent OR variable decelerations lasting < 60 seconds with a rapid return to baseline, with normal baseline and moderate variability.

Equipment for EFM

  • Devices for External Monitoring:

    • Ultrasound transducer (measures FHR)

    • Tocotransducer (measures ctx)

  • Devices for Internal Fetal Monitoring:

    • Fetal scalp electrode (FSE)

    • Intrauterine pressure catheter (IUPC)

Evaluating Electronic Fetal Monitoring Strips

  • Normal FHR:

    • 110-160 bpm

  • Variability:

    • Fluctuations in baseline FHR reflecting fetal autonomic nervous system function requiring adequate oxygenation.

    • Variability definitions:

    • Absent: undetectable

    • Minimal: ≤ 5 bpm

    • Moderate: 6-25 bpm

    • Marked: > 25 bpm

  • Accelerations:

    • Represent temporary increases in FHR noted as 15 x 15 or 10 x 10 in preterm.

    • Reassuring indicators reflecting responsiveness of the CNS and absence of acidosis.

  • Decelerations:

    • Represent periodic decrease in fetal heart rate.

    • Types:

    • Early Decelerations: Gradual decrease in FHR, nadir occurs with peak of ctx (result of head compression).

    • Late Decelerations: Subtle appearance; nadir occurs after ctx peaks (caused by placental insufficiency).

    • Variable Decelerations: Abrupt decreases and increases in FHR (caused by cord compression).

    • Uterine activity should be assessed for frequency, duration, intensity, and resting tone to mitigate risks and ensure adequate monitoring.

Nonreassuring Fetal Heart Rate Assessment

Categorization of FHR Assessments

  • Normal (Reassuring):

    • Normal baseline, moderate variability, absence of decelerations besides early decels, acceleration presence = CATEGORY 1

  • Indeterminate:

    • All tracings not categorized as Category 1 or 2 = CATEGORY 2

  • Nonreassuring:

    • Absent variability, recurrent late decelerations, recurrent variable decelerations, bradycardia, sinusoidal pattern = CATEGORY 3

Nursing Responses to Nonreassuring Fetal Heart Rate Patterns

  • Identify the cause:

    • Evaluate FHR patterns and assess maternal vital signs.

    • If indicated, perform SVE (sterile vaginal exam).

  • Medications and Procedures:

    • Stop oxytocin or other uterine stimulants as needed.

    • Terbutaline may be ordered for tocolysis.

    • Reposition the patient and increase IV fluids to enhance placental perfusion.

    • Administer 8-10 L/min of oxygen via facemask.

    • Consider using internal monitors depending on the situation.

  • Documentation Responsibilities:

    • Keep provider updated on FHR patterns, interventions taken, fetal and maternal responses, and orders received.

    • Be prepared for urgent delivery if signs of severe nonreassuring patterns occur.

Preterm Labor Management

  • Definition:

    • Labor occurring between 20 weeks and 37 weeks gestation.

  • Conditions Increasing Risks:

    • Maternal conditions such as infection, diabetes, chronic hypertension, drug use, connective tissue disorders, and previous preterm births.

  • Symptoms of Preterm Labor:

    • Cramping, low back pain, increased discharge, pelvic pressure, changes felt in the abdomen, and a sense of pressure in the vulva/thighs.

  • Medications and Treatments:

    • Betamethasone or Dexamethasone given to enhance fetal lung maturity reduc signifying respiratory distress syndrome.

  • Tocolytic Medications:

    • Magnesium sulfate for neuroprotection, Nifedipine and Indomethacin for tocolysis, and Terbutaline as an adjunct when indicated.

Drug Guidelines for Preterm Labor

  • Betamethasone:

    • 12 mg IM for two doses 24 hours apart to accelerate fetal lung maturity.

  • Dexamethasone:

    • 6 mg IM every 12 hours for four doses for similar effects.

  • Magnesium Sulfate:

    • Used for neuroprotection and can be given for tocolysis, regular monitoring of serum levels is essential.

  • Terbutaline:

    • Administered subcutaneously or via IV with strict evaluation for maternal heart rate and blood pressure responses.