This is a big change in a child's life especially if he or she has been the only child so it is normal for some children to be anxious.
Create this experience into a positive and exciting time. Have conversations about babies, visit friends with babies, read stories about babies and talk about how your family is growing.
Reflect on what your toddler was like as a baby and some of the things that happened. Include your child in preparations and give them some ideas about how they can be involved in caring for the new baby.
Ensure you prepare your child if you have a hospital stay after having the baby. Have a 'significant other' care for your child and ensure the routine is kept the same.
When the baby comes home ensure you also spend quality time with your toddler in the adjustment period. They may also like to look after their own baby doll. Provide resources such as a small cradle, baby nappies, bottles etc. Role playing helps young children make sense of the world.