I gained only one pound during my first pregnancy and gave birth to a 7 pound, 7 ounce daughter.
With my second pregnancy, I gained three pounds and gave birth to a 7 pound, 12 ounce son.
After my first pregnancy, I did weigh less than I did before I got pregnant. Immediately after my second pregnancy, I actually weighed MORE when I was discharged from the hospital than I did when I was admitted (thanks to all of the fluid they pumped my body full of). I lost weight quickly, though, thanks to breastfeeding:)
I am now 35 weeks pregnant with my third child, and right now I weigh less than I did when I got pregnant.
I am slightly overweight, and with each pregnancy have had a little extra weight when I got pregnant. However, I do not diet during pregnancy-I eat healthy, well balanced meals.
I hope this helps!
EDITED TO ADD: I do not recommend TRYING to keep your weight down. Eat healthy, and take what comes because the baby's health is more important than how much weight you gain or do not gain!