Hello. It is best to wait until at least her second heat. Usually a Pom will go into heat the first time at under 1 year of age. Their bodies are still developing at that age, and the stress of carrying pups and whelping can be detrimental to their health and development. Additionally, as they still need all the nutrients that they get, and the pups will need a great deal of nutrition while in utero, either mom or the pups (generally both) will suffer malnutrition during the pregnancy. Please research thoroughly before breeding your Pom. You'll be better able to keep her safe and healthy. Also, it's always a good idea to consult your vet prior to breeding.