I asked about it before my op as I thought I would be on at the time of my op. Nurse said it’s fine. There’s nothing you can do about it anyway, it’s all about mother nature!! 
I would get some Always ultra night, cause they’re nice and big!! I wouldn’t wear a tampon though.
Turns out that I came on a week before my op anyway!! Must have been stressed!!
Hope it all goes well for you hun x