Inability to concieve or to take the pregnancy to term is known as infertility. It is the incapacity to procreate (reproduce) live offsprings. Failure to ovulate, abnormalities of heat cycle (estrus), failure of breeding (copulation) and pregnancy loss, any of these conditions can cause infertility in a female dog.
To be fertile, a female dog needs to have normal estrus cycle, and ovulation of healthy eggs into a healthy reproductive tract, followed by fertilization of those eggs by healthy sperm. Furthremore, the embryos need to be planted in the uterine wall, develop into normal fetuses and delivered alive at the end of gestational period. Progesterone concentration must remain steady throughout the pregnancy for it to be successful. Any abnormality during this whole process can result in alteration of the reproductive process which can lead to infertility.
Common symptoms associated with infertility in female dogs include
Failure to cycle
Prolonged time between heat cycles (prolonged inter-estrous interval)
Abnormally frequent heat cycles (inter-estrous interval of 4 months of less between heats)
Silent heats (no obvious outward signs of vulvar swelling or bleeding)
Split heats
Failure to allow the male to mount and breed
Failure to achieve a tie during mating
Failure to conceive despite normal copulation
Failure to carry a pregnancy to term
Reabsorption or mummification of puppies
Abortion
