Fetal Surveillance

Question 1

What is a general approach for foetal surveillance?

Answer 1

• pick up placental insufficiency (last half of pregnancy)
• Hx - foetal movements
• Exam - fundal height (cm, absolute, serial) - top of uterus to symphysis pubis (30 weeks, 30cm - it equates)
• Ix:
  
  • biochemical test - no longer done. (placenta makes oestriol).
  • US
  • CTG

Question 2

What are you looking for on fetal US?

Answer 2

• foetal biometry = size + growth
  
  • absolute
  • serial
  • head abdominal ratio
• amniotic fluid volume
  
  • amniotic fluid index
  • sum of vertical depth in all 4 quadrants
  • N = 7-20
• foetal activity
  
  • breathing
  • tone - flexed fine (wrist joint)
  • movements
• Doppler
  
  • umbilical artery
    
    • can measure ratio of peak systolic velocity + end diastolic flow (high resistance diastolic affected more than systolic)
      
      • stepwise from normal to reduced - to low to reversed.
    • hypoxia constricts placental arterioles (responsive vessles). Hypoxic lung go to good bits constricts, placenta is the fetal lung.
    • can’t measure flow because unknown vessel calibre (twisted).
  • MCA - middle cerebral artery

Question 3

What are the features you want to look at in CTG?

Answer 3

• measure of fetal HR over time - just rate.
• Baseline - normal is 110-160
• Variability - normal is 5-25bpm
  
  • speeds up as breath in due to increase VR. Sinus arrythmia is the variability. Not the same but imbalance between sympathetic and parasympathetic
• Accelerations - 2x15bpm in 20minutes
• Decelerations - none if normal

Question 4

What are some causes abnormal CTG variability readings? Give some examples.

Answer 4

• Causes: 4 Ss
  
  • sick = hypoxia
  • sleeping
  • sedated
  • submature
• Variability:
  
  • increased - hypoxia (>25bpm)
  • reduced - submature, sick, sedated (narcotics), sleeping
  • absent - terminally hypoxic
  • sinusoidal late deceleration - anaemic (rhesus), 160mls fetal blood in circulation - extravasated

Question 5

What are some deceleration alterations? What do they correspond with?

Answer 5

• Early declerations: normal
  
  • rapid onset rapid recovery - fine head compressions (contraction simultaneous)
  • reactive early declerations at contraction. variability reduced - morphine narcotics in labour
• Late declerations
  
  • due to hypoxia - fetus is diverting blood to brain and heart and away from skin and gut. There is a delay.
• Variable declerations
  
  • cord compression - baroreceptors. Straight down and straight up.
  • cord squashed with each contraction.
  • Classified severe - deep and wide and rebound tachy (above baseline) (hypoxic) - mild to mod okay
• Prolonged declerations
  
  • sustained hypoxia - crashed. HR with sustained bradycardia. Due to:
    
    • sustained cord compression.
    • abruption
    • maternal hypotension (fix - rest need deliver)
      
      • epidural with inadequate prehydration
    • sustained uterine contraction

Question 6

CTG Classification?

Answer 6

• reactive - reassured
• not-reactive (no accelerations, reduced variability) - investigate
  
  • reduced variability - sleeping, sedated, sick (hypoxia)
  • Ix using an US - fetal activity, doppler (umbilicus)
• critical - deliver (absent variability, sinusoidal pattern)
  
  • C-section - need it now, also uterine contraction reduction in uterine placental blood flow (labour could take too long).

Question 7

Fetal arrythmias?

Answer 7

• ectopic beats - in hypoxia
• heart block -
  
  • Sjorgen’s - anti-Rho antibodies bind to the heart in the bundle of Hiis in fetus. Genes switched on and off during life - e.g. Fetal Hb. Changing protein expression. Damage to cardiac myocytes.
• straight line
  
  • reentry arrythmia - no autonomic control. Flutter with 2:1, SVT. Fixed rate.
  • NTD (neural tube defect) - aencephaly - not having a brain - no automic activity