I had/have a huge ovarian cyst that delevloped in my first trimester that caused MAJOR weight gain from fluid. I was about 145lb pre pregnancy and jumped to 160lb just before I found out but it turned out to be a HUGE 10cm by 10cm fluid filled ovarian cyst. Since end of first trimester I am down to 157lbs and cyst is down to 5cm by 5cm and baby now weighs 11ounces at 19 weeks!!!! (already a big baby like his/her brothers)
I go by the difference from prepregnancy to now which is +12lbs. I'm certain some is still guild from the cyst but baby is healthy and I am slowly losing bad weight and fluid and picking up healthy baby weight. Doc is not worried and I am being monitored for the cyst.
until this pregnancy, i have been rather slim (not skinny but not fat, a healthy 135-145 at 5'3") i gained about 55lbs with #1 and 40lbs with #2 but i have never topped 160 in my life (when i got close i was pregnant) so I'm a little worried about gaining too much this time around :/