Why do some mothers commit maternal filicide?

Most times maternal filicide occurs when the mother is mentally ill or insane. There are some other reasons  that mothers commit this crime. Some mothers hear voices in their heads telling them to kill their children. That is an example of a mother being insane. Another reason is mothers believe that it is in the best interest of their kid if they die. In some cases mothers don't mean to kill their children but they abuse their children too much. Although it may start off as just abuse after sustaining a large amount of it the child may die. Another way mothers commit the crime which is very unlikely is when mothers kill their children in order to get back at their husband. Euripides showed this in his play Medea when Medea killed her children to get revenge on Jason her husband. Also some mothers kill their children because they are a burden on their lives. However no matter how this happens it is wrong and should never occur.