Yep, I have to agree with bringing it up with some sort of time frame. My guess is that you've hinted about it but haven't really given a firm time frame on when you would like any of this to happen because you wanted to see his reaction first. Fair enough!
But now's the time to say "The clock is ticking and I'd like to have a baby by X date for X reasons". Then give him time to digest it and actually think about it properly. And when I say time, perhaps a couple of weeks?
I'd also say "I'll give you a couple of weeks to think about it" so that he KNOWS that you won't be pressuring him in that time and that he can use that time to really come to terms with the idea.
That way he's not pressured but he knows what you're expecting and when you're expecting it. He might decide he's not into it, but that's when discussion and compromise comes in. Men just like the absolute of time frames sometimes and that way it's not up in the air while you wait for him to decide .