The whole inside is blown up, the hormones are out of wack. To spay at this time, will mean the dog will be under anesthetic longer because the increased size and blood in the area -- lots of bleeders to tie off. The surgery is much more complicated.
Complications to spay surgery, because of its location, can also mean complication to the bladder function and urinary incontinence. I do not have any correlations between spaying during a heat cycle and spay-related urinary incontinence though.
I wouldn't risk it. It is up to you. I have never used them, but I hear boys undies, use a sanitary napkin, and put the tail through the fly.
My bitches are ok with the doggy diapers.
Jenna, RN CGC & Babs, CD RA CGC HIC
Heidi, RA CGC
SG3 Odessa, SchH1, Kkl1, AD
Ninja, RN CGC & Milla, RN CGC
Joy, Star Puppy, RN CGC
Dolly CGC & Bear CGC