How long does it take to straighten up a bathroom at least well enough that you wouldn't be embarrassed to let your pregnant friend use it? It's not like she's the Queen of England or Martha Stewart or the photographer from House Beautiful or something.
For me? Well, the downstairs toilet is at the back of the house, so first, depending on the day and how I've been travelling, I'd have to clean up the hall way, and the lounge and then the dining room, and the kitchen, and the laundry including all the clothes on the floor there, but my toilet is cleanish, so say 3-4 days to get it to a point that I wouldn't be worried they'd injure themselves. I am a very messy person and sometimes my house is worse than others depending on my workload, my son and whether I have enough energy to clean (I have an illness that makes me extremely tired so that going to work usually uses all the energy I have in a day)
As an example, while watching the boston bombers being hunted they announced on TV that the police would be going house to house searching for him inside and out. I realised that if that ever happened to me I would demand to see their warrant and then refuse them entry, not because I believe in my civil rights or anything, but because I would prefer the chance of a homicidal maniac over the embarrassment of having the police enter my home when it is at it's worst. At least the homicidal maniac isn't expecting it to be clean and I'm not inviting him in.
So absolutely I would refuse entry to a friend if there was any other option for them. And I have refused entry to my mother when she asked to use the toilet once as she is the most judgmental person I know. If there was no other option and it was a bad mess day, I'd probably let them in but may never contact them again due to my embarrassment.