Prenatal Monitoring

Cardiotocography

(Fetal heart rate monitoring)

Baseline Fetal Heart Rate 110-160bpm

  • With moderate variability of 6-25bpm

    • < 6bpm - minimal variability

    • > 25bpm - marked variability

Acceleration

  • ↑ FHR >15bpm lasting > 15secs (>10 for 10secs if < 32wks)

  • Well oxygenated and healthy fetus has spontaneous and temporary ↑ in HR

Deceleration

  • ↓ FHR >15bpm lasting no more than 3mins (>3mins is bradycardia)

Early Deceleration

  • Contraction ➔ fetal head compression ➔ vagal stimulation

  • Gradual deceleration that is synched with contraction

Late Deceleration

  • Placental insufficiency

  • Deceleration begins after contraction

Variable Deceleration

  • Umbilical cord compression (fetus pushes against or grabs cord)

  • Abrupt, < 30secs (2 boxes) from onset to nadir

  • ± decelerations temporal association with contractions

Non-Stress Test

  • Reactive/Normal

    • > 32wks gestation: > 2 accelerations in 20 mins

    • < 32wks gestation: >10bpm lasting > 10secs

  • Nonreactive

    • No acceleration or < 15bpm (sleeping, immature, compromised)

      • Do biophysical profile or contraction stress test (with oxytocin)

Contraction Stress Test

  • Reaction of FHR to uterine contractions provoked by oxytocin

Biophysical profile (BPP): 10 points

  • Noninvasive test (after ~28wks) evaluates risk of antenatal death

    • Non-stress test: 2 points

    • US findings (2 points each):

      • Fetal movement: > 3 movements within 30 mins

      • Fetal tone: > 1 extension and flexion

      • Fetal breathing: > 1 rhythmic breathing > 30 secs within 30 mins

      • Amniotic fluid volume: Deepest pocket - vertical > 2cm, horizontal > 1cm

BPP points:

  • ≥ 8 points: no signs of fetal compromise

  • 5–7 points: unclear risk of fetal compromise, repeat BPP in 24hrs

  • ≤ 4 points: potential fetal compromise, delivery indicated