So you're getting a little nervous about becoming a parent... no surprise there. After all, you're embarking on basically the biggest adventure known to man. Not to add to the pressure or anything. But seriously — ignoring the fear isn't the way to deal with it. In face, that will only make it worse. A better idea is to talk about it with your mate.
Start by figuring out what your concerns really are. Are you worried about losing your freedom... or your sex life? Scared you won't be a good parent? Dreading going back to work or leaving the job? Whatever it is that you're feeling, try to communicate it to your partner. Then, ask him about his own anxieties. Once you've both gotten the fears out of your heads and into words, chances are, things will seem a lot less scary. And, you might be surprised to find that the two of you actually (probably) share some concerns.
By sharing your deepest feelings rather than erecting a wall, you'll strengthen your emotional intimacy and find yourselves better prepared to handle your soon-to-arrive new addition — as a couple.