Abstract: Abstract: Objective To determine whether high serum homocysteine (Hcy) and low folate and vitamin B12 levels are correlated with the clinical index of neonatal hypoxic ischemic encephalopathy(HIE). To provide the reference for the diagnosis and treatment of neonatal patients with HIE. Methods Totally 94 cases of neonatal patients with HIE(32 mild，40 moderate, and 22 severe) treated by Tianjin children's hospital from April 2010 to April 2011 were enrolled.The control group is 20 cases of neonatal patients with neonatal swallowing syndrome over the same period.The serum levels of Hcy, folate and vitamin B12 were compared between four groups. Results The serum levels of Hcy, folate and vitamin B12 have statistical differences in four groups (P＜0.05). Compared with the control group, there were higher levels of Hcy and lower levels of folate and vitamin B12 in HIE groups. The Hcy levels in HIE groups increased with the deterioration of HIE. Serum levels of vitamin B12 in severe group are lower than those in the moderate group（P＜0.05）. Condusions The Hcy serum levels of neonatal patients with HIE have certain reference value in the assessment of the severity of HIE. To give timely supplementary folate and vitamin B12 neonatal patients with HIE may play an active role in the process of the treatment.

Key words: cysteine, homocysteine, hyperhomocysteinemia, hypoxia-ischemia, brain, folic acid, vitamin B 12, asphyxia neonatorum, infant, newborn