Seizures occurring in a newborn are often caused by lack of oxygen to the fetus during labor and delivery, which can occur because of:

• Metabolic disorders
• Infections
• Developmental disorders
• Trauma
• Difficulties in delivery

SOURCE: http://www.hopkinsmedicine.org/neurology_neurosurgery/specialty_areas/epilepsy/pediatric_epilepsy/neonatal-epilepsy.html