Backstory: I have two very well bred, cutting bred, mares.  Smart, gritty, athletic little mares. Unfortunately, they come with cow horse height/size, as well as no proper nutrition until they were 4 years old. Both top out between 13.2-14 hands on tip toes. I love them both, but I don’t think either will end up doing much in the barrel pen with adults due to their size. Just on pedigree alone, I think they would make A+ broodmares prospects, but I am not sure how small is too small to breed. I don’t want them to produce anything huge  I would be happy as a clam with 14.1-15 hands  I like the shorties, obviously. ??

If embryo transfer isn’t currently an option, would breeding mares that size be safe? How should I navigate this option for their future? I’m new to even the possibility of breeding and very curious to hear from those who know more than me. Thank you! 

Their ability to carry a foal is a non-issue.  The issue I see is the marketability of a 13...h horse once full grown.  The barrel horse world is cheap and picky.  Plus most see cutting blood as a deterent as well.  

I would be nervous breeding a mare that small. I bred my 14.2 hand mare to a 15.2 hand stud and the resulting filly is now 5 and topped out at 14.1 hands. God forbid if my mare had been any shorter. That being said, if they were not properly fed then they might not have reached the height they genetically should have. So you never know what you might get. But if it were me, I wouldn't do it. If you try to offset their height by breeding to a tall stud, then there might be complications. 

Thank you for the quick replies! If we did breed them, it would most likely be for our own personal use (with the understanding that life does happen and that marketability does have to come into play eventually). Both mares are from lines that I personally love and would like to continue to keep around for myself. I guess I’m just more worried about safety of the mares and ability to carry foals. Both sets of both parents were in the 14.2-15.1 hand range if that has any bearing. 

I had someone want to breed a POA to my 15.1 stallion last year.  There should be no problem with anything. The foal will be smaller because of genetics. 

One never knows. I remember Molly Swanson running a 1/2 welsh pony named Pecan at the NFR more than once. That little mare was quick. I'm guessing she wasn't over 14.2. She made the nfr with Molly more than once. There are people out there that love some cutting in a pedigree. 

Her mama was MAYBE 14 hh... on a good day. Bred to a 16hh stud and this was the result. She's probably 14.2 and smaller than I would like, but your mare should be able to handle breeding to a big stud no problem. 
https://www.allbreedpedigree.com/too+smart+ta+streak

My 14 hand barrel mare is a 1D horse.  Doesn't matter the size of the pen.  I bred her in 2015 and she had no problems foaling.  I did choose a stud that was not tall (Blazin Jetolena @ 14.3 hands), but I did that for a specific reason-I like my horses short.  I don't have one horse over 14 hands tall.  Also, you may hear that small horses may not be marketable in the barrel industry......parents looking for their children will not overlook them, and they make wicked pole horses :)

well my good mare was 5 hands on her tip toes, her momma was 15 hands. my mares mother was bred to the same stallion like 6 times, all the fillies where 15 hands and stout and the geldings where 16plus hands. that stallion threw big horses especially the geldings. maybe breed to a stallion who usually throws bigger babies.  it is hard to sell a little horse no matter 1-d or not. if keeping for self fine.