"n these circumstances the Church began to feel uneasy about the communion of persons who might not be able to swallow the host. "
This was my first thought. How does one deal with an infant who 'spits up' the consecrated host. As for dipping fingers in the Sacred Blood and placing it in the mouth of an infant to suckle ... well, I believe that the introduction of microbiology probably nixed that practice.
It is not uncommon at all to see women in line for communion with a 3 month old infant.
So it is the mother who determines when an infant is old enough to commune?
No, sorry. I was not clear. Infants and on up receive communion just after they are baptized and chrismated. Usually the baptisms and chrismations are done on a Saturday and they commune the next day at liturgy.
Let me ask today at church about your excellent question, about spitting up. I know that Saint John Maximovitch once ate the Mysteries that a woman spit up (who had rabies, I think) after taking it to her in the hospital.