Fetal Assessment Techniques

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Fetal Movement Counting - Daily Kick Count

  • Maternal method to screen fetal well-being, usually from 28 weeks.
  • "Count-to-Ten" (Cardiff):
    • Feel 10 movements. Normal: within 2 hours.
    • Report if: <10 movements in 2 hours, or no movements in 12 hours.
  • Sadovsky: Count for 1 hour (TID, post-meal). Report if <3 movements/hour.
  • ↓ Movements: Investigate with NST/BPP.

⭐ Fewer than 10 movements in 2 hours is a key indicator for further fetal assessment.

Non-Stress Test (NST) - Happy Heart Traces

  • Evaluates fetal well-being via Fetal Heart Rate (FHR) accelerations with fetal movements.
  • Reactive (Term ≥32 wks): ≥2 accelerations of ≥15 bpm lasting ≥15 sec in 20 min. (📌 15-15-2 rule)
  • Reactive (Preterm <32 wks): ≥2 accelerations of ≥10 bpm lasting ≥10 sec in 20 min. (📌 10-10-2 rule)
  • Non-Reactive: Criteria not met in 40 min. Requires further evaluation (e.g., Biophysical Profile - BPP).

⭐ Most common reason for a non-reactive NST is a fetal sleep cycle.

Reactive Non-Stress Test (NST) trace

Contraction Stress Test (CST) - Uterine Challenge

  • Assesses fetal heart rate (FHR) response to uterine contractions, indicating uteroplacental reserve.
  • Requires 3 contractions (each ≥40s) in 10 min (spontaneous or induced via oxytocin/nipple stimulation).
  • Interpretations:
    ResultFinding
    NegativeNo late or significant variable decelerations.
    PositiveLate decelerations with ≥50% of contractions.
    EquivocalIntermittent late/variable decels; or decels with hyperstim.
    Unsatisfactory<3 contractions in 10 min; poor tracing.

Fetal Heart Rate Decelerations

⭐ A positive CST is associated with an increased risk of fetal distress in labor, IUGR, and low Apgar scores.

Biophysical Profile (BPP) - Fetal Five Score

Assesses fetal well-being. 5 parameters, 0 or 2 points each. Max 10. 📌 BATMN.

ParameterNormal (Score 2)Abnormal (Score 0)
Fetal Breathing (FBM)≥1 episode ≥30s/30minAbsent or <30s/30min
Gross Body Moves (GBM)3 distinct moves/30min<3 moves/30min
Fetal Tone (FT)≥1 active extension/flexionSlow ext/flex, or absent
Amniotic Fluid Vol (AFV)MVP >2cm or AFI >5cm & <25cmMVP ≤2cm or AFI ≤5cm
Non-Stress Test (NST)ReactiveNon-reactive
  • Score 8-10: Normal. Low risk. Repeat as indicated.
  • Score 6: Equivocal. Repeat 12-24h. Deliver if oligo/term (≥37wks).
  • Score ≤4: Abnormal. High risk. Deliver.
  • Score 0-2: Severe compromise. Deliver STAT.

⭐ BPP is a better predictor of fetal pH than NST alone, especially in IUGR.

Biophysical Profile Scoring Criteria

Doppler Velocimetry - Vascular Vibes

Non-invasive assessment of fetal blood flow, placental function, and fetal well-being.

  • Indices: S/D Ratio ($S/D$), PI ($(S-D)/Mean$), RI ($(S-D)/S$).
VesselParameterNormalAbnormal & Significance
UAS/D, PI, RIS/D <3.0 (post 30wk)↑Indices (placental insufficiency); AEDF/REDF (severe IUGR)
MCAPI, PSVHigh resistance; CPR (MCA PI/UA PI) >1↓PI (brain sparing); PSV >1.5 MoM (anemia); CPR <1 (risk)
DVPI, 'a' waveForward flow↑PI, absent/reversed 'a' wave (cardiac decompensation)

⭐ Umbilical Artery REDF (Reversed End-Diastolic Flow) indicates severe fetal compromise, often necessitating urgent delivery.

High‑Yield Points - ⚡ Biggest Takeaways

  • Reactive NST (≥2 accelerations) is reassuring; non-reactive needs BPP or CST.
  • BPP score ≤4/10 indicates fetal compromise; 8-10/10 is normal.
  • Positive CST (late decelerations) suggests uteroplacental insufficiency.
  • Oligohydramnios (AFI <5 cm) is a key concern for fetal well-being.
  • Absent/Reversed End-Diastolic Flow (AREDF) in umbilical artery Doppler is ominous.
  • MCA Doppler PSV is crucial for detecting fetal anemia.
  • Normal FHR variability (5-25 bpm) indicates good fetal oxygenation.

Practice Questions: Fetal Assessment Techniques

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A 3-4 month old baby with heart rate 250/min, QRS complex less than 0.07 sec and no P wave, Diagnosis will be :

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Flashcards: Fetal Assessment Techniques

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Fetal macrosomia : Macrosomia is defined by birthweight e _____ g by ACOG

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Fetal macrosomia : Macrosomia is defined by birthweight e _____ g by ACOG

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