If they are pregnant, they might be having a harder time holding their bladder and if they are very comfortable or asleep, sometimes accidents happen. Once that smell gets onto the couch, they associate it as being a place to "go". Are you planning on spaying the girls? Positive reinforcement is the best way to go with training a dog not to do something. That's one thing about dogs that some might call an advantage over cats. Most of them respond more to verbal commands such as "down", "no" and "stop". my dog tells me when she needs to go out. Pay attention to their body language. My dog and I are like Archie and Edith Bunker after 12 years together. we get on each other's nerves but we love each other. You might have to look up the reference depending on your age
Willowy, do you know why dogs purposely urinate on the couch while pregnant? My males don't pee in the house hardly ever. Maybe once every two or three years do the males pee in the house. As far as the females are concerned, all the unspayed ones urinate on the couch. Any reason why? This is the point I tried to get across.