On average that's a dead child every two weeks at this institution. How does something like that go unnoticed?
It part of a well-oiled forced labour camp system, shielded by a conspiracy between church and state, that's how.
Unmarried mothers would be considered sinners and would be sent to one of these institutions by their own families on many occasions. They would deliver their children, who would be forcefully separated from them and placed in the care of the nuns, to be put up for adoption later. The women, meanwhile, would be forced into slave labour to repay the "favour" to the nuns. If they were lucky, they got out after a year or two. If they weren't, they'd be sent to the Magdalene Laundries, another kind of concentration camp where they'd be enslaved sometimes for the rest of their lives, subject to horrific abuse.
The mothers wouldn't even try looking for their children, the families wouldn't care and no-one even thought about asking questions. Since the camps were allowed to work in relative isolation from the outside world, disposing a few hundred dead children would have been easy, as long as it was done within camp grounds, behind high walls.
Ireland: the place where the systemic abuse of children isn't nearly the worst thing the Catholic Church has been permitted to do.