Baptists are all over the place regarding the proper subjects of baptism. While denying access to the covenant community to babies due to a lack of matacognitive ability, they are quick to stress, on other occasions, the mercy of God towards the mentally handicapped, the still-born, and dying infants. Am I missing something here? Does "cake and eat it" come to mind?
The confessional Reformed approach is far more consistent. For instance, according to 1 Cor. 7:14:
For the unbelieving husband is made holy because of his wife, and the unbelieving wife is made holy because of her husband. Otherwise your children would be unclean, but as it is, they are holy. (ESV)
According to the passage, children of believers are 'clean'. That is a word shot through with covenantal overtones. Therefore, children of believers are covenantally accepted. There can be no other conclusion from this passage. For believers grieving over the death of a child, there is hope; hope that the child is clean and with the Lord in glory. This is why King David was so confident that he would see his dead son again (2 Sam. 12:23). Reformed theology is at least consistent as to why believers' children who die go to be with the Lord.
The other side of the passage is less hope-giving i.e. "otherwise they would be unclean." All that the Reformed can say about children who die outside of the covenant is that they are in God's hands and that the judge of all the earth will do what is right.
If Baptists really want to be consistent, they should affirm, (contra 1 Cor. 7) that ALL children are unclean and that they are unsure of the fate of ALL those who die in infancy.