FYI with dogs it is called a HEAT CYCLE not a menstrual cycle...and it can start typically between 5 to 10 months depending upon the health and breed of the bitch. Usually by age 6 months a bitch is of a good safe age and weight to have her SPAYED so as to prevent irresponsible breeding! Spaying also will cut way back on her getting Breast Cancer or any of the other reproductive cancers that kill bitches. Remember your girl has no real interest in becoming a "Mommy" the hormones alone cause the desire to breed, not what she is "thinking or feeling!" Spaying also means that you have joined up to help prevent more beautiful dogs from being put to death! There are over one thousand dogs killed weekly in the USA due to a lack of good people to give them forever homes! The Heat Cycle runs like this: 1. Pro-estrus (swelling of the vulva, clear discharge to start which then becomes bloody. Some may have more swelling and less blood, others more blood and less swelling. Some larger breed bitches show almost NO external signs. During this time the bitch is attractive to dogs, but may not be receptive to breeding at all! The phase lasts typically 8 to 13 days) 2. Estrus (Normally the bleeding has stopped the vulva is less turgid, but still swollen. There may be a clear or straw-colored discharge. NOW the bitch may seek out dogs and will usually accept them. It lasts 4 to 7 days.) 3. Metestrus (False pregnancy may occur during this time; or puppies may be growing from a successful breeding. 6 to 10 weeks.) 4. Anestrus (The quiet period of variable duration when there is no activity in the bitch's reproductive tract. Generally 15 weeks...give or take.) Please help us stem the tide of deaths and improve your own girl's future health as well!

A female dogs menstural cycle starts when she is six months old