Adverse short- and long-term outcomes among infants with mild neonatal encephalopathy.

Background: Studies in newborns with mild neonatal encephalopathy (mNE) demonstrated normal outcomes, but recent literature suggests otherwise.

Methods: This retrospective cohort study examined inborn infants between 2014 and 2017. Biochemical and clinical characteristics determined the presence of NE and an encephalopathy score categorized infants as Definite or Possible mNE. An Unexposed control group consisted of newborns not meeting the inclusion criteria. Long-term outcomes assessed included cerebral palsy, seizures, developmental disorder, and motor and speech delay. The association of mNE with seizure disorder by 3 years of age was assessed with logistic regression and developmental disorders with Cox proportional hazards models.

Results: Of the 156,501 births, we identified 130 with Definite mNE and 445 with Possible mNE (0.8 and 2.8 per 1000 births, respectively). Both groups had significantly higher rates of any developmental disorder and motor and speech delay when compared to the Unexposed (p < 0.05, except for p = 0.07 for motor delay in the Possible NE group). The Definite mNE group had higher rates of developmental disorder and motor and speech delay when compared to the Unexposed with hazard ratios (95% CI) 2.0 (1.2-3.2), 3.7 (1.5-8.8), and 2.1 (1.3-3.5), respectively.

Conclusions: An estimate of short- and long-term consequences of mNE suggests that there may be a higher risk of adverse outcome.

Impact: Infants with mild NE are at significant risk for adverse short- and long-term outcomes. The risk of having an abnormal long-term outcome at 3 years of age were doubled in the mild NE group compared to the Unexposed group. Randomized clinical trials are needed as neuroprotective strategies may mitigate these.