Baby Fever.

I'm almost 27 and in a very serious relationship.  We're unofficially engaged and plan on being married within the next year, just haven't bought a ring yet.  However I have very serious baby fever.  For the first two years of his life I raised my nephew, 100% with little to no help from his mother.  She now has him and is wonderful with him. But I can't seem to fill that void.  I want babies of my own. My SO aren't quite financially ready for babies yet however.  He's still in college full time.  How do you ladies without children cope with the baby fever??