From the nspcc site:
"•On average, every week in England and Wales one child is killed at the hands of another person.
•On average, 52 children in England and Wales are killed at the hands of another person every year.
•Over two thirds of children killed at the hands of another person in England and Wales are aged under five years.
•Infants aged under one year are more at risk of being killed at the hands of another person than any other single year age group in England and Wales.
•Every ten days in England and Wales one child is killed at the hands of their parent. In over two thirds (67% on average) of all cases of children killed at the hands of another person, the parent is the principal suspect"
The killing of a child is and always has been quite a common event, it should be noted this is far far from a new trend and links to the national statistics can be accessed from the nspcc site to see the background
http://www.nspcc.org.uk/inform/research/statistics/child_homicide_statistics_wda48747.html
anyone with mental health issues or personal tragedy in their lives would have my support however in cases like this my sympathy can only go out to the children, irrespective of the circumstances we are all capable of seeing help for our offspring and nothing in this womans personal life can explain her actions.