Key result
Category III fetal heart rate tracings linked to ~45-fold greater odds of neonatal encephalopathy.
Why the study?
Are specific fetal heart rate characteristics prior to delivery associated with the development of neonatal encephalopathy in singleton, non-anomalous infants at ≥36 weeks' gestation?
Case-Control (n=342)
Blinded to outcome
No
Are specific fetal heart rate characteristics prior to delivery associated with the development of neonatal encephalopathy in singleton, non-anomalous infants at ≥36 weeks' gestation?
Odds Ratio: 44.99 (95% CI 7.23–279.97)
Absolute Event Rate: 17.4% vs 0.9%
Category III fetal heart rate tracings and specific characteristics such as bradycardia and decelerations prior to delivery are strongly associated with the development of neonatal encephalopathy.
OBJECTIVE: We sought to identify fetal heart rate (FHR) characteristics that are associated with neonatal encephalopathy (NE). DESIGN: Retrospective case-control study. SETTING: A single medical centre in Shanghai, China, 2006-2015. SAMPLE: Women delivering a singleton, non-anomalous infant at ≥36 weeks' gestation diagnosed with NE (cases, n = 109) were compared with a group of women with unaffected infants (controls, n = 233). METHODS: Two physicians blinded to the outcome independently reviewed FHR tracings during the last 30 minutes of tracing prior to delivery. FHR characteristics were compared in the two groups and multivariable logistic regression was used to adjust for confounding. MAIN OUTCOME MEASURES: Adjusted odds ratio (aOR) and 95% confidence interval (CI) for the presence of specific FHR categories and characteristics. RESULTS: Category II FHR tracings were observed in 89% of women prior to delivery and were not independently associated with NE. Notably, a category III FHR was observed in 17.4% of women in the NE group compared with 0.9% of women in the control group (aOR 44.99, 95% CI 7.23-279.97). Bradycardia, minimal/absent variability, late decelerations and prolonged decelerations were independently associated with NE, whereas accelerations were protective. Similar findings were found when the cases were limited to NE with arterial cord pH <7.1 and in a subgroup analysis of women with category II tracings. CONCLUSIONS: Category III tracings, while infrequent, are not uncommon prior to delivery among fetuses who develop NE. In contrast, most FHR tracings are category II prior to delivery; however, individual FHR characteristics within this category are associated with NE. FUNDING: This research was supported by the Interdisciplinary Programme of Shanghai Jiao Tong University. TWEETABLE ABSTRACT: Category III tracings are not uncommon prior to delivery among fetuses who develop neonatal encephalopathy.
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Frey et al. (2018) conducted a case-control in Neonatal encephalopathy (n=342). Category III fetal heart rate tracings vs. Control group (unaffected infants) was evaluated on Neonatal encephalopathy (aOR 44.99, 95% CI 7.23-279.97). Category III fetal heart rate tracings prior to delivery were strongly associated with neonatal encephalopathy, observed in 17.4% of cases compared with 0.9% of controls (aOR 44.99; 95% CI 7.23-279.97).
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