Speaking as a mother who has two biological children, finding out about the first one was disbelief, followed by 'this isn't real', and ended with 'Oh, my God!' when I felt the baby move for the first time. It was followed by a heck of lot of impatience. With the second child, who was planned, impatience came first. Then incredible and total joy when the pregnancy was confirmed.
Also, as a mother of two adopted children, fear tops the list until you're holding the final adoption papers. We were excited to become parents again, but anxious to have the final decision on paper. Both our adoptions were private ones, so the wait wasn't as bad. And with a four year age difference between all our children, each time we had to reconcile our feelings over becoming 'new' parents again. With our last son, we had to buy everything new having long gotten rid of all our baby items after firmly stating we were done expanding our family.
Simply stated I think we've been through every emotion there is. It all depends on the circumstances involved. Obviously with adoption there's at least a bit of planning involved and probably the earnest desire to be parents. But I'd still imagine anxiety, fear, and curiosity to overwhelm any parent who adopts.
Hope this helps.