Should you decide to breed your female, you should not attempt this until at least her second or third heat. The female is still growing at the time of the first heat, and she is not physically prepared for the rigors of raising a litter. To prevent an unspayed female from mating during her heat period, you will need to take some precautions. Never leave her unattended outside, even if tied, as males will go to great lengths to get to her. This is especially important in the middle of her cycle when she will accept and encourage a mating. To prevent the local males from discovering that she is in heat, take her away from her immediate surroundings to relive herself, as the urine of a female dog in heat gives off a scent that is particularly attractive to male dogs. It is best to take her out in the car to a park or public spot, being very careful, always, to contain her on a leash and clean up all solid wastes. This may sound like a lot of trouble, but it may keep the male from congregating around your house in the hopes of getting to your female.
Many people feel it easier to board the female in heat at a local kennel until the season is over, but this is by far the most expensive alternative. If you should choose such an option, be sure to make it clear that the female is in heat and must be kept separated from all mates.
Your veterinarian can supply you with pills that will reduce the odor of the urine during the heat period. There are also other items on the market to prevent the bloody discharge from staining household items or clothes, although most females in heat are very meticulous and tend to keep their genitals very clean.
Spaying is the permanent alternative for preventing a mating and should be considered if other preventive methods seem troublesome.