That men often suffer as a result of another's sins has been shown over and over in the Bible: "Cursed be Canaan" for his father Ham's sin (Gen 9:25), 36 men died for Achan's covetousness (Josh 7), Eli's descendants lost the high priesthood to another Aaronic family because he failed to restrain his sons (1Sam3:13). Sin is an asteroid strike in the ocean with death and disease rippling outward and drowning innocent and guilty alike. So, babies and other innocents die or suffer horrid diseases because we keep sin and death active in the world, "and so death passed unto all men, for that all sinned" (Rom 5:12).
No other event illustrates the one to one consequences of a sin causing the death of an innocent baby more clearly than the death of David's baby son. After Nathan confronted David, "Thou art the man," one of the judgments he pronounced was, “However, because by this deed you have given occasion to the enemies of the LORD to blaspheme, the child also that is born to you shall surely die.” (2Sam 12:14). David sinned; the baby died (vs 19).
About a thousand years later, another son of David was born innocent and lived and innocent life (2 Sam 7:14ff). He died a horrible death despite his innocence. It was totally unfair for this innocent lamb to suffer at all, just as it was unfair for the baby to die for David's sin. Jesus died for us, the innocent for the guilty. How easily the old phrase rolls of our tongues and through our minds His death transcends all the unfair deaths of all the innocents before and since for this son of David was the Son of God.
If I never understand why babies die, I know God loves me because he killed his Son that I might live (Acts 2:23, 3:18, 4:28, Jn10:18). More than I want answers to the injustices in a sin-sick world, I want to go to the place where that love is.
Beloved, let us love one another, for love is from God, and whoever loves has been born of God and knows God. Anyone who does not love does not know God, because God is love. In this the love of God was made manifest among us, that God sent his only Son into the world, so that we might live through him. In this is love, not that we have loved God but that he loved us and sent his Son to be the propitiation for our sins. (1John 4:7-10).