Question on Infant Baptisms?

Infant baptism was practiced when infant and childhood mortality rates were very high. During the height of the middle ages, it sometimes spiked a fifty percent. You were baptized as a baby just in case you never reached maturity. If you did reach maturity, there was a ceremony when you confirmed (or not) the decisions made for you by parents. Would want to have told grieving parents that their babies wouldn't be going to heaven because they didn't reach an age to make the decision for themselves?