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Cardiotocography as a Test of Fetal Well Being

Cardiotocography as a Test of Fetal Well Being. Max Brinsmead PhD FRANZCOG July 2012. The objective of CTG screening:. An ideal screening test:. CTG as a screening test. CTG as a Screening Test. Positive predictive value = the chance that a screen positive individual will have the disease

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Cardiotocography as a Test of Fetal Well Being

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  1. Cardiotocography as a Test of Fetal Well Being Max Brinsmead PhD FRANZCOG July 2012

  2. The objective of CTG screening:

  3. An ideal screening test:

  4. CTG as a screening test

  5. CTG as a Screening Test • Positive predictive value = the chance that a screen positive individual will have the disease • For CTG this is never more than 50% • i.e. at least 50% of the time it will be unnnecessarily alarming

  6. A screening test is more likely to be a true positive if

  7. A screening test is more likely to be a true positive if It is positive in a high risk group

  8. So always consider the clinical context

  9. And be prepared to back up with a diagnostic test

  10. Which, for the diagnosis of fetal hypoxia, is Scalp Blood pH or lactate

  11. Problems with Screening: • FALSE POSITIVES • And the resources required to deal with them • UNREALISTIC EXPECATATIONS • i.e. misunderstanding about the sensitivity of the test

  12. Meta analysis of RCTs of Intrapartum CTG monitoring • 12 Trials • In 10 centres in the US, Australia, Europe and Africa • 58,855 women and 59,324 babies • Both high and low risk pregnancies • Compared routine EFM with intermittent auscultation

  13. Meta analysis Results • A significant decrease in: • rate of 1 minute Apgar scores less than 4 (RR = 0.82 and CI 0.65 - 0.98) • Neonatal seizures (RR=0.50 and CI 0.32 - 0.82)

  14. Meta analysis Results • A significant increase in: The rate of intervention by Caesarean section and operative delivery (RR=1.23 and CI 1.15 - 1.31)

  15. Meta analysis Results • No effect on: • rate of 1 min Apgar scores <7 • rate of admissions to NICU • Perinatal death rate • 5 min Apgar scores • rate of Cerebral palsy

  16. But let us not throw out the baby with The CTG’s dirty bathwater!

  17. Because, as a screening test for hypoxia, IT IS CURRENTLY THE BEST TEST WE HAVE

  18. An Examination of CTG Abnormalities What is Important

  19. CTG Features • Baseline heart rate • Decelerations - early, late and variable • Short term variability • Accelerations

  20. Reassuring CTG • Baseline 110 – 160 bpm • >5 bpm variability • No decelerations • Accelerations present (The absence of accelerations in an otherwise normal CTG is of uncertain significance)

  21. Non Reassuring CTG • Baseline 100 - 109 or 161 - 180 bpm • Variability <5 bpm for <40 but <90 min • Early decelerations • Variable decelerations • Single prolonged deceleration up to 3 min

  22. Abnormal CTG • Baseline <100 or >180 bpm • Variability <5 bpm for >90 min • Atypical variable deceleration • Late deceleration • Prolonged deceleration >3min • Sinusoidal for >10 min

  23. Atypical Variable Deceleration • Slow return to baseline • Secondary rise in baseline • Biphasic • Loss of variability during deceleration • Continution baseline at a lower level

  24. RCOG Recommendations Settings on CTG machines should be standardised, so that: • Paper speed is set to 1 cm/min • Sensitivity displays are set to 20 bpm/cm • FHR range displays of 50–210 bpm are used.

  25. Categorisation of CTGs • Normal =A CTG where all four features fall into the reassuring category • Suspicious =A CTG with one non reassuring feature • Pathological =A CTG with two or more nonreassuring features or one or more abnormal features

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