Intrauterine resuscitation during the second stage of term labour by maternal hyperoxygenation versus conventional care: study protocol for a randomised controlled trial (INTEREST O2)

Table 1 Classification of cardiotocograms according to the modified International Federation of Gynecology and Obstetrics criteria

	Baseline heart frequency	Variability Reactivity	Decelerations
Normal CTG	• 110–150 bpm	• Accelerations • 5–25 bpm	• Early uniform decelerations • Uncomplicated variable decelerations (loss of < 60 beats)
Intermediary CTG	• 100–110 bpm • 150–170 bpm • Short bradycardia episode < 100 bpm for > 3 minutes < 80 bpm for > 2 minutes	• > 25 bpm (saltatory pattern) • < 5 bpm > 40 minutes	• Uncomplicated variable decelerations (loss of > 60 beats)
	• A combination of two or several intermediary observations will result in an abnormal CTG
Abnormal CTG	• > 170 bpm • Persistent bradycardia < 100 bpm for > 10 minutes < 80 bpm for > 3 minutes (without an increasing tendency)	• < 5 bpm for > 60 minutes • Sinusoidal pattern	• Complicated variable decelerations with a duration of > 60 seconds • Repeated late uniform decelerations
Pre-terminal CTG	• Total lack of variability (< 2 bpm) and reactivity with or without decelerations or bradycardia

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