Peculiarity of preterm neonates at 33-35 weeks gestational age with mild-to-severe hypoxic-ischaemic encephalopathy: a single-centre experience.

To describe the peculiarity of preterm neonates at 33-35 weeks gestational age (GA) with mild-to-severe hypoxic-ischaemic encephalopathy (HIE). This single-centre retrospective study compared the background characteristics, treatments, and outcomes of 30 preterm HIE neonates at 33-35 weeks GA with those of 399 HIE neonates at ≥ 36 weeks GA between 2011 and 2023. Between the 33-35 weeks and 36, 37-40, or ≥ 41 weeks GA groups, HIE severity and use of therapeutic hypothermia (TH) were not significantly different. Between the 33-35 weeks and 37-40 weeks GA groups, no TH, except for mild HIE, was significantly different (35% vs. 3%) and the incidence of moderate-to-severe magnetic resonance imaging (MRI) injury was significantly different (43% vs. 19%); the white matter injury was predominant. Moderate-to-severe MRI injury was associated with lower GA (odds ratio 0.81 [95% confidential intervals, 0.67-0.98]), but total adverse outcomes, including death before discharge and long-term outcomes over 2 years, were not significantly different among the groups and were not associated with GA.

conclusionIn this study, preterm neonates at 33-35 weeks GA, some of who were unable to receive TH because of reasons, except for mild HIE, were at risk of moderate-to-severe MRI injury, but their total adverse outcome was comparable to that of preterm neonates at ≥ 36 weeks GA. Further research including mild-to-severe HIE regardless of TH are needed. WHAT IS KNOWN: ・TH for preterm neonates at 33-35 weeks GA with moderate or severe HIE does not affect neurodevelopmental outcomes at 18 months. ・TH for preterm neonates with moderate or severe HIE may not increase neurodevelopmental impairment compared with term or near-term neonates. WHAT IS NEW: ・Preterm neonates at 33-35 weeks GA with mild-to-severe HIE were at risk of moderate-to-severe MRI injury, but death and long-term outcomes over 2 years were comparable to those of preterm neonates at ≥ 36 weeks GA. ・Some preterm neonates with moderate or severe HIE did not use TH because of poor conditions.