[jeanief]

Split heats occur when a bitch grows follicles on her ovaries and experiences the signs of pro-oestrus (swollen vulva, vulvar bleeding, attractiveness to males) but does not progress into oestrus and does not ovulate. The bitch's follicles will usually regress, and then she will come into a complete heat cycle with ovulation anywhere from two to 12 weeks later. Split heats are most common in a young bitch, especially at her first season, and are not considered to be associated with infertility when bred on the cycle in which ovulation occurs. Split heats must be differentiated from short inter-oestrous intervals between two true heat cycles. A vaginal smear will show red blood cells and intermediate and superficial cells as would be expected during pro-oestrus but in a split heat will not progress into an oestrus smear. ( I found this on the internet ) sorry, I didn't see the same article was posted