This is the second time I have mated my bitch. Had progesterone tests done before mating and sire is proven and been fertility tested.
Not sure if she is pregnant or not still another couple of weeks to wait but given the first time failed I am not holding out much hope this time round.

How many times to you try before simply saying its not going to happen?

Just as an aside my friend's little cross breed bitch was caught at the park and is now pregnant.......it all seems a bit unfair!!

Are you trying to mate her to the same dog? Sometimes it just doesn't gel and you have to try a different dog.

I would not try the same dog more than once, but certainly would try the bitch with another dog, with aid of p5rogesterone testing, after all they are not machines, and certainly get pregnant far more often on the first go than we do.

I certainly have had bitches miss.  with a few it was using a dog with waning fertility, but on other occasions I am sure the season was 'off' and perhaps the bitch didn't ovulate.

My misses have usually been with older bitches on subsequent litters. 

I'd suggest a thyroid test to check the bitch's levels. It's a simple straight forward blood test and it's amazing how a slightly lower level can affect fertility.
Just a thought but it worked for a friend of mines Hungarian Vizlsa, she missed 3 times to 2 different proven dogs and did have premate tests. She now gets 1, 0.8mg soloxine everyday and had a litter of 10 earlier this year. Luckily they found this out before she was too old to have a litter.

I would have said breeding a bitch (or a male for that matter) with a thyroid issue not ideal at all.
Especially when it may have a hereditary basis and her 10 offspring may now be at risk of
developing hypothyroidism.

I thought the same myself. 

I would never go beyond adjusting mating time with trying to get a bitch in whelp, anything else causing issues is likely to be storing up problems for future fertility (health) in your lines. 

This would include behavioural issues such as a bitch that won't be mated, or unwarranted aggression (beyond maidenly reluctance, requiring reassurance) to the male, or one that once bred from shows poor mothering traits.

Having this discussion at the moment on a US board for my breed.

So many ONLY do AI breeding claiming most Repro vets recommend it "on so many levels".....yeah their bank accounts most likely up there as number one.
Funnily the same breeders are raving on about ONLY Natural feeding.

You reap what you sow with breeding dogs in the long run.

Even worse those who advocate routine elective C sections, so they know when to plan for the birth and increase survival of pups/reduce still borns. 

What about the poor bitch being subjected to needless abdominal surgery???

But of course the reason they have such success with AI is they opt for surgical implantation which our vets consider unethical.

I am one of four generations who are hypothyroid myself. No question that it is hereditary! It really isn't a simple little problem that is solved by a hormone replacement. Depending on the level you are affected you can end up like my mother who developed heart problems directly linked too it.

I wouldn't wish the behaviour problems my dog has had due to being hypothyroid on anyone

>I would have said breeding a bitch (or a male for that matter) with a thyroid issue not ideal at all.

Great minds think alike.  I scrolled down and see that ethically, we're all singing from the same hymn sheet.