My first pregnancy... I gained almost 40 pounds and didn't exercise. I began to because I was given a membership when I was first pregnant. I went twice and never went back!! I paid for it too. I can't believe how I looked when I was pregnant. Obviously you need to gain weight but sometimes too much is too much for certain people. For me 40 pounds was way too much.
Second pregnancy. I didn't formally exercise but did play a little bit of tennis here and there and had to walk up 3 flights of steps every day to our apartment. I don't know that my eating habits were different but I gained between 25 and 30. Do you factor in the 5 pounds that you lose in the first tri???

My advice is to do SOMETHING. Not necessarily anything formal, but remain active. Do the stuff your'e supposed to do like taking the steps, walking when you can, etc. It makes a huge difference.
I had wanted to lose 10 pounds before getting pregnant as an experiment because when my son was born (2nd baby==1st wasn't breastfed because it was a surrogacy), I lost all of my pregnancy weight within two weeks. Maybe I didn't gain enough eh? However he gained a pound per week himself until he was 2 months old, then it tapered off.
Within that first year I lost another 10 pounds without doing anything. I was one of the lucky boobie moms who lost weight and I was thanking God every day let me tell you!!!
So I thought this time let me lose some weight prior to and see if I ever get to know what it's like to be skinny lol

Silly I know but who hasn't thought about it?
Take care,
Karen