My dog is in her first season, just entering the 4 days receptive period.  While I understand that a bitch will urinate more frequently at this time to attract mates, is it normal for a house trained bitch to wet inside?  She's done it three times today!

Some bitches will mark, and often seem less able/willing to hold their water.

I have noticed over the years if we have a  pee accident it is when a girl is in season.

I suppose al the swelling there will also give her mixed sensory signals.

> is it normal for a house trained bitch to wet inside?

Yes.  I've seen it many times when a bitch is in season.  It's nothing to do with them "forgetting" their house training.

My adult has not had an accident since a tiny puppy and on his season she has had 2 accidents which is so unlike her, thankfully she's on her way out now

That's interesting Suejaw - my Ellie (nearly 11) had 2 or 3 accidents with her last season, having never ever done it before. Weird aren't they!!