It can be quite difficult for your child to initially digest the fact that you are having a new baby. Sharing your attention and care is without a doubt the most difficult part to go through by your child. It is essential to prepare him mentally and emotionally before the arrival of the new baby.
Give enough time to your child to realise that there will be several changes within the family. Reassure him that the newborn will not be taking his place but he should nonetherless make some space for him in the house. Your elder one would like to be aware of what will still be his, like his toys, his room,etc, and what he will have to share.
The most sensitive part of the journey would be when the mum comes home with the newborn. The child could throw tantrums or show signs of regression behaviour to vent out the frustration, in his cleanliness or eating and feeding habits.
In this type of situation, jealousy is a common phenomenon : it should not be much of a worry, but it has to be ensured that this feeling of jealousy is taken care of by giving the maximum amount of time and attention as possible to your little one without his new baby brother or sister.