Decapitated Baby's Mom Seeks Revenge

by Brian
(Carlisle, Pennsylvania, USA)

I'm looking for an Italian (?) horror movie produced sometime prior to 1991 involving a mother who gives birth during a storm, and a glass pane breaks and decapitates her baby.

Several years later, all the doctors involved in the delivery and the mother are killed by someone using a decapitation machine (a motor attached to a plastic wire). Throughout the rest of the movie, the woman's husband tries to determine who the killer is.

In the end, it turns out the mother faked her death and is actually the killer.

Any thoughts?