John Piper believes that infants who die go to heaven. I posted my thoughts on this topic not too long ago in a post titled Do Babies Go to Heaven? . In my post, I used the character of God and 2 Samuel 12:15-23 to defend my belief that babies who die go to heaven.
Piper bases his argument on Romans chapter 1, which states that all people will be judged on what they can know about God. Since babies, and also those with mental disabilities, do not have the ability to “know” certain things to be true, they cannot be judged on this basis. If you are interested in Piper’s thoughts on this topic, I have provided a link to both the audio and the video below.
Audio: http://www.desiringgod.org/ResourceLibrary/MediaPlayer/4541/Audio/
Video: http://www.desiringgod.org/ResourceLibrary/MediaPlayer/4541/Video/
Theologically Speaking 
In reality, we simply don’t know about the fate of “every” baby? But, we can know those of the, or in the Covenant of Grace. The children of those in covenant and faith themselves, i.e. “the Election of Grace” (Rom. 11:5 / Rom. 9). My thoughts anyway.