I probably gained about 10 lbs. per IVF cycle after everything was said and done. But, I had OHSS, too.
BUT...I will say, that I stopped exercising, and really stopped watching what I was putting in my mouth. So I might not be the best example of what a 'normal' weight gain might be.
When I was finally pregnant (with twins) after my 3rd IVF...after they were born, I actually weighed 10lbs less than my starting weight. Go figure...
I am still trying to lose that 10-20lbs I would like, to feel good physically and emotionally.