BACKGROUND AND PURPOSE: 

• Frey et al. (BJOG, 2018) sought to determine if fetal heart rate (FHR) characteristics, specifically category III, were associated with neonatal encephalopathy (NE)

METHODS: 

• Retrospective case-control study 
  • Women delivering a singleton, non-anomalous infant ≥36 weeks’ gestation 
  • Emergency cesarean without labor were excluded  
  • Cases: Women whose infants were diagnosed with NE  
    • ICD10 codes and maternal/neonatal chart review  
    • Definition based on ACOG and AAP Task Force recommendations 
  • Controls: Women whose infants were unaffected
    • Frequency matched to cases by year   
• Two MFM physicians blinded to the outcome independently reviewed FHR tracings  
  • On admission that was on average 60 minutes duration  
  • During the last 30 minutes of tracing prior to delivery 
  • NICHD/ACOG guidelines for reading and interpreting FHR tracings  
• Primary outcome  
  • Presence of specific FHR categories and characteristics

RESULTS: 

• 109 in the NE group | 233 in the control group 
• More women in the NE group had category II or III tracings  
  • NE: 54.1% category II | 3.7% category III  
  • Controls: 18.9% category II | 0% category III  
• Category II FHR tracings were observed in 89% of women prior to delivery and were not independently associated with NE 
• Category III FHR prior to delivery was observed in 
  • 17.4% in the NE group  
  • 0.9% in the control group  
  • Adjusted odds ratio (aOR) 44.99; 95% CI, 7.23–279.97  
• NE was associated with 
  • Bradycardia 
  • Minimal/absent variability 
  • Late decelerations (any and recurrent)  
  • Prolonged decelerations 
• Accelerations were protective of NE 
  • aOR 0.35; 95% CI, 0.21-0.58 
• Similar associations were found when the cases were limited to subgroups  
  • NE with arterial cord pH <7.1  
  • Category II tracings

CONCLUSION: 

• Category III tracings are overall uncommon, but seen in approximately 17% of NE infants  
• Most FHR tracings in NE cases were category II prior to delivery 
  • Some individual characteristics were associated with NE  
• The authors support the current 3 tier system, suggesting that future research should consider further discrimination among category II tracings  

Obstetric interventions will not prevent all cases of NE; however, our data suggest that there is an association between certain EFM patterns and this clinically important neonatal outcome.

Learn More – Primary Sources: 

An evaluation of fetal heart rate characteristics associated with neonatal encephalopathy: a case‐control study

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