Thanks so much for the comments, its good to hear from someone outside my little circle of friends and family.
I'm 27 and I have been married for 3 years now. I'm having a baby cravings. I've always wanted to have a baby. My husband and I planned to start trying once we've been married 5 years. That was a realistic time frame for us. As we are still enjoying our "baby-free" life. I got pregnant back in March, 2006 (not planned). We were ecstatic. It ended in a miscarriage, but ever since then, I've been wanting a baby. I don't think necessarily there is an appropriate age for your clock to tick and for you to have urges. But, I do know almost anything can trigger a baby craving. At least for me. It's just good that you realize now is not a good time. You will know when the time is right.
I don't think it is the body so much at 23 (you're not up against biological deadlines yet) as sometimes it has to do with what else is happening in one's life and how satisfying it is. If someone is about to get their big break in Hollywood or to run for office with a good chance of success, that is not the time when they start craving babies. When things are not so exciting, babies can creep into the subconscious as a way to solve this.