I don't think it's fair in any situation to trap a man into having another baby married or not. Young or old.. be prepared to live with your own consequences if he'd decided to leave you for this. Men are dumb when it comes to contraception so that's not a good enough excuse. My nan felt this way because in her perception she was the one doing all the work anyway. A family member of my oh has done so and is happy with his subsequent child now too and doesn't know it wasn't an accident as such. But eventually he can't turn round and say he doesn't want to look after the fourth, financially, mentally as it wouldn't be fair. Planning a baby really is something in my opinion you both decide on so that consequence could impact the first three kids too. It's entirely up to you what you do with your body just tell him when you are prepared to accept his response which could go either way, we don't know your husband like you do.