My 1 year old female english mastiff and my male english mastiff have been together and I heard it is unsafe for her to be pregnant this young.what should I do if she is already pregnant?

my 1 year old female english mastiff and my male english mastiff have been together and i heard it is unsafe for her to be pregnant this young.what should i do if she is already pregnant?
My 1 year old female english mastiff has already been with my male . What should I do if she is already pregnant?

If she has been in season, likely it is too late to do much except have a vet check her for injury, infections, etc. I find such carelessness disappointing.