ok, so I made this horse fertile and bred her to this horse
10 turns later no foal, so I turned again twice. Still nothing. Checked the horses page and it says nothing about her being pregnant, etc so I go back to the stud to try again. When I try to breed her again I get this message
'error, this horse is already pregnant'
I suppose I could try aborting but not sure if that would work or not.
Edit - aborted foal worked and got foal on second try, sorry guys