Speaking as a male I cannot begin to understand how anyone could do this let alone a mother. There's no conclusion been drawn by the police yet but it seems obvious what's happened.
Why on earth do people think that it is getting more common. Infanticide is actually decreasing, probably in no small part due to better recognition of mental health and as much as people dislike them, improved social services.
Clearly in cases like this women have gone completely insane, that doesn't mean we should empathise with her. It goes against all natural instincts not to protect your children.