I gained from clomid for 9 cycles. Although my 15kg weight gain before DS2 was mainly from depression resulting from infertility and m/c. So maybe it isn't just the drugs but the state of mind women are in by the time they end up in IVF.
I'm sure I'll be told I'm making excuses for myself but that's why I gained the weight. I ate my pain. I know it sounds cliched but it really is true.