Ticking

I noticed something recently. I have a biological clock. It's ticking.

It happens everytime I see a baby. I think "Wow... I could have one of those and raise it properly". I'm not seeking to actually have a baby now, but I'm fairly confident that I'd make a great mother. What could be better than having a small person to cultivate and love? I "get" why people want kids. I'm worried that "not ready" will suddenly turn into "too late". I could bear children later in life in theory, but will I actually be able to? Fertillity dips signifigantly after age 25 in most women. I know I want to have an established career first, and a husband (although I'm certainly not going to wait forever if he doesn't come along). But then what if those things take too long?