Hi Guest,
You should try contacting your breeder if you got your pup from a responsible breeder who takes care in their breeding, does the necessary health testing for your breed, occasionally breeds healthy dogs as close to the standard as possible and takes the time to follow up on their puppies.
If this was not the case then you should contact the Breed Club Secretaries for WHWT.
There is no hurry for this if your bitch is only 18 months as you have given yourself time to take your bitch to shows to get the opinion of judges as to whether she is of good enough standard to breed from and get any necessary health testing done. Then when she is over twenty-four months of age you can consider whether you wish to take the risks of breeding from her to produce puppies.
WHWT's are often produced by puppy farmers so dogs from these backgrounds should not really be re-produced.
Christine