Also mammary tumors are a risk.

My dog had bleeding for a month and then she went through a month of false pregnancy (most dogs do) it was miserable for both of us. I had an appointment to get her spayed but then she went in the heat and I had to reschedule it. Then we had wildfire smoke. she was in pain. she blew her coat really bad, nearly bald in places. she got fussy and was reactive. my neighbor's intact male dogs were slobbering at the door, and a couple of big pit bull dogs went after her aggressively while I had her on leash at the park. 6 months later we had a blizzard so I am grateful that I got her spayed and I didn't have to deal with that during a blizzard. She's a service dog so regularly going in heat isn't good.

some people were laughing at me at the store - I was looking at re-usable doggy diapers, like the kind toddlers wear. They didn't understand and were "why would anybody buy that for their dog?!" ...Me: "oh, they're functional, it's not dress-up or anything. Dogs have a period that lasts weeks so they need several pairs that can be re-washed. they can bleed enough to soak it and need changing." then dogs get false pregnancy after that for several more weeks. she almost needed a bra. ouch.