I've put on 7lb so far. I wasn't a big carb eater before pregnancy and maintained/lost weight by eating this way. First tri was awful, the only thing I could stomach was carbs. I have PCOS and insulin resistance so as soon as I up the carbs, the weight piles on. Since reaching 2nd tri, I have now (under midwife/drs advice) gone back to my lower carb eating habits, I feel great, heartburn has disappeared, loads of energy, stable appetite etc. I haven't put on any weight now for 3 weeks.
I was "fluffy around the edges" (read as "bigger than id like) before pregnancy with a BMI of 29.6 and could really do without piling on 3 stone before baby arrives - i'm hoping to keep my gain around the 20lb mark.