Fetal Monitoring

    Overview

    • Symphysis Fundal Height (SFH) 
      • 20-31 weeks = gestational age (GA), 32-40weeks +2 = GA
    • Wt Gain
    • Maternal Serum Screen (MSS) (16 weeks for spina bifida)
    • Ultrasound (see below)
    • Non-Stress Test (NST) (20 min HR monitor)
    • Contraction Stress Test (give oxytosin)
    • Chorionic Villus Sampling
    • Amniocentesis

    Fetal Monitoring

    Ultrasound Anatomy

      • Early: r/o ectopic
      • 12 weeks: Nuchal fold
      • 18-20 weeks: fetal anatomy + dates
      • Later: Growth, placenta location, fetal wellbeing (BPP)
      • IUGR Screen:
        • 10-25% mid IUGR
        • <10% moderate IURG
        • <3% severe IUGR
        • Head Circumference / Abdominal Circumference
          • Until 34wks --> HC > AC
          • After 34wks --> AC > HC
      • First Trimester Scan - r/o viability, r/o ectopic, # of fetuses+chorionicity, nuchal translucency (NT)
      • Complete Obstetrical Scan (18-20 week scan - anatomy)
      • Third Trimester Scan - Some order, no proven benefit, identifies position, placenta etc..

    Doppler Flow Studies

      • UA - Umbilical Artery
        • Growth-resticted fetuses
        • End-diastolic flow most important (if absent need admission +/- delivery)
      • MCA - Middle Cerebral Artery- If fetus in trouble, will decrease resistance in brain, causing incr diastolic flow  (identifies fetal anemia)
      • UTA - Maternal Uterine Artery - if increased resistance, RF for uteroplacental vascular insufficiency (IUGR) and preeclampsia

    Biophysical Profile

      • Fetal Movement (2) - 3 discreet body or limb movements
      • Fetal Tone (2) - One limb extension and back to flexion
      • Fetal Breathing (2) Least important - 30s of breathing (diaphragm movement, kidneys, or abdo wall)
      • Amnionic Fluid Volume (2) Most important, if low, do NST - Single pocket 2x2
        • Largest pocket <2cm OR
        • Amniotic fluid index <5cm  (add two largest pockets) (also measure fluid in each quadrant - variant?)
      • Total: /8
      • Total (with NST) /10

    Non-Stress Test (NST)

                    Must be >28 weeks, measures whether the fetus is getting adequate oxygenation.
      • 20 min monitor of fetal heart rate (FHR)
      • 2 accelerations of 15bpm, lasting 15 sec = normal (supposedly represents fetal movement)
        • Reactive (normal)-
          • 1.  presence of ≥2 fetal heart rate accelerations lasting 15sec within a 20-minute period (with or w/o fetal movement)
          • 2.  beat-to-beat variability +/-5bpm is normal (symp vs. parasymp well developed). (if not, abnormal)
          • 3.  Absent decelerations
        • Nonreactive-
          • 1.  presence of <2 fetal heart rate accelerations within a 20-minute period over a 40-minute testing period.
          • 2.  No beat-to-beat variability
          • 3.  Spontaneous decelerations.

    Oxytocin Contraction Stress Test (OCT)

      • Stimulate 3 contractions in 10min --> observe decelerations (late decels are bad)
      • Now replaced by BPP

    Scalp pH

      • Take via vagina small amount of blood from fetal scalp
      • Meaning
        • <7.20 = fetal acidosis (deliver!)
        • 7.2-7.25 = repeat 20-30min
        • 7.25-7.35 = normal
      • Poor accuracy, lots of false positives

    Fetal Heart Tracing

    • Baseline (must have minimum 2min, otherwise indeterminate)
      • Good baseline: 110-160bpm
      • Tachycardia: In presence of good variabiliy, not a sign of distress.  May be increase in fetal activity.  Causes:
        • Maternal Fever, fetal hypoxia, fetal anemia, amnionitis, tachyarrhythmia.
    • Variability
      • Variation in cycles more than 2 cycles/min... indication of sympathetic/parasympathetic responses working well
      • Measure variability peak-to-trough:
        • Minimal <5bpm
        • Moderate 5-25bpm
        • Marked >25bpm
      • Poor variability is a bad sign...fetal distress
    • Accelerations:
      • <32 weeks defined as 10x10 (10bpm over 10s)
      • >32 weeks defined as 15x15
      • 2 accelerations of 15x15 over 20 minute period = reactive NST (good sign)  98% of fetuses have it by 34 weeks.
      • If no reactivity/accelerations, can try scalp stimulation
    • EARLY: Head Compression
      • Come with contractions
      • Mirror contractions
    • VARIABLE: Cord Compression
      • Grabs the cord or shoulder compresses it against something
      • 15bpm x 15sec
                
    • LATE Deceleration (Serious)
      • Starts with contraction + prolonged after contraction
    • SUSTAINED Decelerations (Most Serious)
     
    • Treatment
      • Call for help
      • Stop oxytosin
      • I.V. Fluid Bolus (Improves blood volume, flow, oxygenation)
      • Oxygen - face mask, prongs
      • Maternal left side (relieves vena cava, increases return to heart)
      • Pelvic exam (Check for cord prolapse, determine stage)
      • Delivery? mode

    Chronic Fetal Distress

    • Long-term
    • Symphysis fundal height (SFH) / Weight
    • Ultrasound (best measure of wellbeing)
    • Causes:
      • HTN
      • Smoking
      • Poor nutrition
      • chromosomal
      • etc.

    Acute Fetal Distress

    • Sudden-onset
    • Fetal heart rate patterns
    • Meconium (green-colored stool)
    • Scalp pH (oxygenation of blood)
    • Causes:
      • Abruption
      • Infection
      • Cord Accident
      • Preeclampsia

    Intrauterine Growth Restriction (IUGR)

    Definition
    1. Infant weight <10%ile
    2. Suboptimal intrauterine growth
      • Oligohydraminos
      • Abnormal umbilical doppler flow
      • Increase HC/AC (head circ/ abdo circ)
    3. Severe IUGR: <3%ile
    Etiology
    • Weights <1500-2500g have 5-30x higher mortality
    • Infants <1500g at term have 70-100x mortality
    • Female infants do better than male
    • Risk Factors
      • Maternal
        • Prev low birth weight
        • Race (black)
        • Substance use, chronic HTN, cyanotic heart/lung disease, hyperthyroidism
      • Placental
        • Placental insufficiency
        • Hypertension/PIH
        • Poor placentation (abruption)
        • Vascular Disease (diabetes)
      • Fetal
        • Congenital abnormalities
        • Fetal Infections (TORCH)
          • Toxoplasmosis
          • Rubella
          • CMV
          • HIV
          • Syphilis
      • Unexplained (50% of IUGR) 
     Stage  Causes  Growth  Result
    EARLY   Infection,drugs, congenital  Symmetric  MSK and organ size affected
    LATE  Poor nutrition, utero-placental  Asymmetric  MSK ok, organ & fat affected
     
    • If happens EARLY in pregnancy: Symmetric IUGR (MSK and organ size affected)
      • No head sparing
      • HC/AC ratio may be normal
    • If happens LATE in pregnancy: Asymmetric IUGR (MSK ok, but organ size & fat are affected)
      • Head Sparing (Biparietal Diameter - transverse head diameter is normal)
      • HC/AC abnormal  (i.e. HC > AC) [see below]
    • Fetal Growth Priority (if hypoxemia/nutrients/renal function or other insult)
            1. Brain/Head
            2. Organs
            3. Skeletal Tissue
            4. Subcutaneous Fat
    • Dx
      • Ultrasound
        • 10-25% mid IUGR
        • <10% moderate IURG
        • <3% severe IUGR
        • Head Circumference / Abdominal Circumference
          • Until 34wks --> HC > AC
          • After 34wks --> AC > HC
      • Progression of fetal insult:
        1. Umbilical systolic/diastolic ratio rises (vascular resistance)
        2. Fetal growth on U/S slows/stops
        3. Oligohydraminos develops  (Largest pocket <2cm OR Amniotic fluid index <5cm [two pockets of fluid add up to max])
        4. Fetal heart rate loses reactivity
        5. Fetal heart rate decelerations
        6. Fetal movement diminishes/stops
        7. Fetus dies
     
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