I wouldn't do it. I have wanted another for ages but DH didn't. Then just at the right time he changed his mind.
I wouldn't want to bring a child into the world through deceit. I don't think it says a lot for the point you are in a relationship if you feel the need to do this. It also isn't the best start for a kid. It is so much better to have a baby when you are both wanting it because gosh it is hard enough even then!