1. Natural or Accidental
(a) Maternal.—Among the maternal causes may be mentioned excessive lactation; any irritation of the rectum or bladder; loss of blood, which, by increasing the amount of carbonic acid in the blood, acts as an excitant to the spinal cord; excessive irritability and excitability of the uterus, &c. Certain states of the system conduce to abortion—albuminuria, syphilis, certain fevers, scarlet fever, smallpox, &c. Abortion may become habitual in some women. Great joy or sudden sorrow have not infrequently been the cause of abortion. The tendency to abortion is greatest at the menstrual periods, that is, at the time when, had not the woman become pregnant, menstruation would have taken place. Slight causes acting at these times are very liable to produce abortion.
(b) Fœtal.—The death of the ovum, or a diseased condition of its uterine coverings, or of the placenta, probably of an inflammatory nature.