Hi there, I haven't yet had a gain due to my * week. In fact I lost 2.5lbs last time.
I know people do, usually because of water retention, and I'm not sure if I've been lucky because I drink a LOT of water (which reduces retention) and have hot water and lemon every morning (it's a diuretic), but even if you do have a wee gain because of hormonal water retention it'll go away without you having to do anything "extra" so you could see a super dooper loss the next week.