(638) Obstetric Antecedent Factors and Therapeutic Hypothermia: Associations with Magnetic Resonance Imaging

Objective: Magnetic resonance imaging (MRI) abnormalities following neonatal therapeutic hypothermia (THT) for hypoxic ischemic encephalopathy (HIE) are associated with long-term neurocognitive impairment. We compared the obstetric antecedent factors among newborns who underwent THT for HIE and had abnormal versus abnormal MRI findings.
 

Study Design: Utilizing ICD-10 codes, newborns at a large teaching hospital with clinically diagnosed HIE and who underwent THT were identified.  Data was extracted from each chart by an obstetrician.  Inclusion criteria for analysis were THT for HIE at > 36 weeks on a non-anomalous singleton newborn, who had a brain MRI during admission.  The MRI was considered abnormal if the following were noted: basal ganglion injury; white matter/watershed-predominant pattern of injury; or, near total injury. A Chi-square test was done with P < 0.05 considered significant.
 

Results: During the 5 year study period (2019-2023), 136 neonates out of 32,765 live births received THT for moderate to severe HIE (4 per 1,000 births). Among them 117 (86%) met inclusion criteria and 28 (23%) had abnormal MRI findings. Nulliparity (P=0.048) and tobacco use (P=0.003) were more common among mothers of those neonates with abnormal MRIs. Fetal heart tracing (FHRT) categorization within 60 minutes of delivery was not significantly associated with neonatal MRI abnormalities (Table 1). Newborns delivered vaginally had a higher incidence of abnormal MRI (P=0.006) compared to those delivered by cesarean. Apgar scores < 5 at 5 and 10 minutes and umbilical arterial base deficit were similar for the two groups.  Small for gestational age neonates were more likely to have abnormal MRI findings (P=0.003; Table 2).
 

Conclusion: Hypoxic ischemic encephalopathy requiring therapeutic hypothermia occurred in 4 per 1,000 births, and among them maternal tobacco use is a modifiable risk factor for abnormal MRI. Fetal heart tracing, Apgar scores at 5 and 10 min, and umbilical arterial acid-base status did not differentiate between abnormal versus normal MRI, a surrogate for long term sequelae.