Backgound: Perinatal brain development undergoes dramatically changing in human life. Multiple insults in perinatal period such as hypoxia or and ischemia, infection and inflammation often cause different severity and patterns of brain injury such as ischemic injury or hemorrahgic injury. To explore the epidemiological rule and correlated risk factors of premature infant with brain injury we used MRI findings to define the diagnosis of brain injury. Methods: The study was prospectively performed on 358 preterm infants from 2008 to 2011at the neonatal intensive care unit of Shengjing Hospital of China Medical University. Detailed Clinical data of all subjects were recorded including: gender, gestation age, birth weight, and the following risk factors: precipiate labor, pregnancy-induced hypertension, fetal distress, multiple pregnancy, prenatal infection, placental abruption, placental previa, gestational diabetes mellitus, prenatal seroid administration, magnesium sulfate, resuscitation history, circulatory disorder, vaginal delivery, early-onset sepsis, mechanical ventilation, blood gas analysis(metabolic acidosis, hyperkalemia, hyponatremia and hypocalcemia). Conventional MRI and diffuse-weighted imaging (DWI) were performed iin 358 preterm infants using 3.0 Tesla MRI scanner. The infants were sedated for imaging with chloral hadrate (50mg/kg). Seriously ill intubated newborn infants were monitored by clinician during scanning and hand-ventilated, and pulse oximetry and electrocardiography were monitored during the procedure. The study protocol were approved by the ethic committee of our university and consented by their parents. All MRI scans were assessed by two radiologists who blinded to neonatal clinical data. The premature infants with brain injury were classified into two groups according to MRI findings: hemorrahgic brain injury and non-hemorrahgic injury (white matter damage). Statistic analyses were performed using SPSS (version 11.5). All data were described as mean±standard deviation. Students't test was used to evaluate the difference in numerical variables. The significance of the difference between premature infants with and without brain injury was tested using the Chi-square test. A logistic regression analysis was performed on factors which found to be significant in univariate analysis. A probability value of P<0.05 was considered statistically significant. Results: There were 128 premature infants with hemorrahgic brain injury (70.7%), and 96 with WMD (53.0%); 43 premature infants with hemorrahgic brain injury complicated with WMD. (23.7%). 21 risk factors were analyzed. Univariate analysis: precipitate labor (X 2=5.295, P=0.021), twin (X2 =4.576, P=0.003), prenatal infection (X2=7.922, P=0.005), circulatory disorder (X2 =5.710, P=0.0017), vaginal delivery (X2=53.624, P=0.000), metabolic acidosis (X2 =13.594, P=0.001), hyponatremia (X 2 =11.691, P=0.001), hypocalcemia (X2 =12.805, P=0.000) for premature infants with hemorrahgic brain were considered statistically significant; prenatal infation (X 2 =5.628, P=0.018), gestational diabetes mellitus (X 2=14.944, P=0.001), magnesium sulfate (X2 =9.248, P=0.002), resuscitation (X 2=6.362, P=0.012), circulatory disorder (X 2=6.341, P=0.012), vaginal delivery (X2 =17.029, P=0.000), metabolic acidosis (X2 =14.944, P=0.001), hyponatremia (X2 =20.242, P=0.000), hypocalcemia (X2 =32.595, P=0.000) for premature infants with WMD were considered statistically significant. Logistic regression analysis: prenatal infection (OR=4.738, 95% CI: 1.201, 18.685, P<0.05), vaginal delivery (OR=9.191, 95% CI: 4.699, 17.979, P<0.05), hyponatremia (OR=3.331, 95% CI: 1.506, 7.366, P<0.05) and hypocalcemia (OR=3.162, 95% CI: 1.325, 7.545, P<0.05) were risk factors for premature infants with hemorrhagic brain injury. Maternal diabetes mellitus(OR=5.211, 95% CI: 1.272, 21.341, P<0.05), vaginal delivery (or=3.078, 95% CI: 1.824, 5.194, P<0.05), hyponatremia (OR=3.331, 95% CI: 1.506, 7.366, P<0.05) and hypocalcemia (OR=4.713, 95% CI: 2.412,9.209, P<0.05) were risk factors for premature infants with WMD. While the prenatal use of magnesium sulfate (OR=0.375, 95% CI: 1.183, 0.766, P<0.05) was an its protective factor. In addition, we did not find the WMD prevalence difference between the premature infants with gestation age less than 34 weeks and the late preterm infants, even the severe diffusive WMD was not unusually found in the late premature infants. Early widespread and diffusive WMD on MRI-DWI often evolved into cystic PVL. Conclusions: Intrauterine exposure including prenatal mother suffering from infection, diabetes mellitus, pattern of delivery and postnatal electrolytes disturbance may contribute to premature brain injury. Prenatal magnesium administration could protect brain from insults. Hierarchy WMD in the premature infants may depend on the severity of insults, but not only on the brain developmental maturation.
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