I think here is a great place to really reinforce that a wonderful relationship is deeper than surface stuff. (appearance, sex drive etc).
Let her SEE (via actions) that your love for her is if anything stronger !
Like Snecail said, it's going to hormonal for awhile, and then you'll be dealing with the little one consuming disproportionate amounts of her time and energy. This is just what kids are about.
Reassure her you expect & understand these things and that your bond will only grow deeper - if maybe in a slightly different manner. But it's all good if you let it be.
You'll hopefully get lots more good advice from the ladies who have actually gone through this.