It drives me crazy too, it doesn't scare me (for some absurd reason, I am not afraid of labour), but it makes me feel like they are belittling me. If I mention wanting a natural, unmedicated birth I get the "that's a great theory, except you have NO IDEA how painful it's going to be, and I'll bet you'll be screaming for the drugs!". And it doesn't just stop at labour, anything I say that is baby related sparks someone to tell me how awful my life is going to be once the baby comes. If I mention looking forward to going trail running I get the "haha, you think you'll have time for that? Well you'll see how little time you have once the baby comes". I mentioned to a friend that I am getting a stroller that has an attachment so I can cross country ski with it, and I was informed that it is a waste of money because that would just be way too much work and I'll never bother doing it. And of course they chuckle at me and tell me "you'll see once the baby comes". I just want to scream at them, just because you might be too lazy to bother using it doesn't mean that I am going to be. And of course I don't know exactly what it's going to be like once the baby comes, just like you didn't know what it would be like when you had your first baby. It will probably be harder and more work than I think it will be, but that doesn't mean that I won't step up to the challenge. I just want everyone to leave me alone and let me figure out things on my own, without laughing at how naive they think I'm being when it comes to my ideas of what I am going to do with the baby or with my life once the baby is born.
End rant.