The term Monstrous has a rich etymology, which includes Moneo meaning warning.
The birth of monstrous children was given in the antics and later a fatal signification. At one period certain phenomena of nature, such as an eclipse or comet, were thought to exercise their influence on monstrous births. Rueff mentions that in Sicily there happened a great eclipse of the sun, and that women immediately began to bring forth deformed and double-headed children.
The death of the imperator Claudius was preceded by the birth of a double monster.
In the beginning of Rome, Romulus forbid to kill abnormals and disformed children but the introduction of the twelve tables changed all as it stated that any monstrous child should be killed instantly.
More generally it was a rule for most abnormals beings to be brutally executed, most often at birth. What is even more sad is the fact that at certain times the oldest people and the weakest children were also gotten rid of because of being a charge for the community.