Retained placenta increases the postpartum interval which is the time between calving and the return to estrus (heat). It also can lead to uterine infection.
Retained placenta is rare in most cow herds. The placenta is retained when the cotyledons on the placenta do not detach from the caruncles on the uterus during parturition. This most often occurs during difficult births (dystocia) in beef cattle. Also, sometimes when cows are induced to calve, you will see a higher incidence of retained placenta in the induced cows.
If afterbirth has not been expelled after 24 hours, contact your veterinarian. Don’t try to forcefully remove the afterbirth.
Retained placenta has been associated with nutrition, in particular, low body condition, low vitamin A or the mineral selenium. Dams giving birth to twins seem to have a higher incidence of retained placenta because in many cases twins are born early. Again, if cows that have been induced calve early, the caruncles and cotyledons are not quite ready to separate, and the placenta is retained.