I'm not even sure what being overweight in pregnancy means exactly. Does it mean being overweight to begin with? Gaining more than you should during? There are all sorts of different guidelines out there about weight and it also seems very individualised.
I was prob 10 lbs overweight when I got pregnant, but then I didn't really gain much the first 5 months (thanks nausea!) The last month or so however my belly has gotten enormous. I don't know if I've gained too much yet but my GP last week said I looked fine (didn't weigh me though) so I'm just not going to worry about it.
A friend of mine who's pregnant started off in great shape (just ran the london marathon) and is eating healthy but for whatever reason has gained a ton of weight. She's really sensitive about it, feels like a failure. I think it would be awful if she had to be weighed all the time and lectured about it. Her baby is doing fine and I'm sure she'll lose all the weight quickly.
On the c-sections, my stepmother was in perfect shape when she had my brother, gained very little weight, and still had to have a c-section because he was so enormous. It doesn't seem quite on to scare women that they'll have to have a c-section if they gain too much weight, when it could happen no matter what you do.
Bottom line, I understand the concerns and it seems to make sense what they're already doing -- monitoring women who are really over or under weight if it seems like they have problems. But I think it would just cause a lot of unnecessary stress if they started micro-managing the weight of every pregnant woman. And they should really be educating ALL women about nutrition and healthy eating, not just women who are overweight.
I've definitely been motivated not to gain too much weight because it just seems like it will make life easier. But I only have so much control over things, ya know? I've definitely tried to be good about eating healthy (no chocolate and crisps over here, sigh) and I'm still looking at cankles for another three months.