When parents are ready to have another child after they have lost one to death, they can never imagine that they are replacing that particular child. So selecting the sex of the one they conceive would only bring disappointment in the long run and that could lead to disaster for the little one who is brought into this.
I find this question offensive. If a child is lost, there is nothing one can do to replace the lost child. Although a new child can be loved, he or she will never be able to take the place of someone else. Even if a child were cloned, it would not be the exact child that had been lost. Each person would have different memories and different histories.