is it something to worry about?  one of my bitches is on day 13 of her season and whilst still bleeding is showing no sign of swelling - she's clearly not 'ready' as yet, but should I be worrying that she's not started swelling as yet?  This is a 'late' season, she was due in January, but this is normal for this bitch.  Thanks

What is normal for her the late season or the lack of swelling?

My girls vary in how much swelling, one of them now retired I used to wonder how her gait looked normal when her vulva was so big for her size.

I presume you plan on mating her, is this her first mating? You won't know if it is a problem till the stud fails to mate with her, on her previous seasons did you make a note of when she seemed to be ready for mating ie tail flagging when you touched her back or saliva testing etc.,not fool proof as they can vary from season to season and reading on here some bitches are nearly at what would be the end of the season before being ready, I had a girl who ovulated on day 6 and ready day 8, no wonder she kept missing as her 2 seasons prior to me trying to get her pregnant showed her to be ready day 11 or 12 by her actions with my male.

just had a bitch in season and all the way through the season she did not swell at all
but she did bleed and my studs where interested in her but no swelling this is the first time i had seen this and she was only a week late in her season it surprised us as we kept watching her and usually around 12 days she is really swollen but not this time

My dearly departed Kizi was very neat in the Lady bits and to all intents and purposes did not swell, her vulva would appear open but no swelling.  She was mated three times and in her first litter had 9 puppies.

This is interesting because my bitch has just finished her 3rd season and she hardly swelled up at all, last season she was very puffy, this time you wouldn't have noticed unless you checked.

being late is normal, although she doesn't normally swell a lot, this time it's non existent.  Yes I would like to mate her, she had a litter last year and came into season on time 4 months later, but was due in again in January, so is late, but last January it had been a year since her last season.... boys were very excited earlier (especially the boy I'm hoping to use) but now aren't so excited and the other breed dog I have who usually howls when the time is right hasn't yet, so I'm still hopeful it may be ok, but it's not looking likely if I'm honest :-( She has been a complete tart - bonking with the girls for a couple of weeks before any blood and standing for anyone immediately, she's been very cute with my neutered boy of a different breed... so no help from her and not really from the boys as yet... thankfully I haven't booked an 'outside' dog this time....

Hopefully all will fall into place when the time is right.

I think that blood tests would be your best bet. I know when I did them it actually showed that the optimum time for mating was before the boys were howling and going mad. They started that behaviour about the time she would have been going  off. This meant that the mating I had last time when the boys had been going mad for a couple of days was likely too late (even though my trollop, sorry little angle was quite happy to stand for the stud) and this is why we had no puppies. Next time I mate her I will be blood testing to make sure I get the right day.

thanks but there's really no possibility of a mating whilst she hasn't increased in size :-( so the optimum time seems irrelevant unfortunately.....

A bitch has come to one of my studs twice now and she never looks to be in season.  Yet the dog managed to mate her and she had 9 puppies each time.  I think you should see if the bitch is presenting to a dog - if she is then the dog will probably find a way!  I find a bitch with a small vulva is often easier to mate than the ones that are massively swollen!

1 of our girls looks small but mated fine too!

My bitch had no trouble being mated even though she was no bigger than when not in season. 

In fact a bitch that is still very swollen can't be mated, (well not comfortably) and it is when the swelling reduces and the area softens that mating can take place.