A peculiar instance is given by Sparkman in which a woman conceived just forty hours after abortion.
Rice mentions the case of a woman who was confined with her first child, a boy, on July 31, 1870, and was again delivered of another child on June 4, 1871.

She had become pregnant twenty-eight days after delivery.

He also mentions another case of a Mrs.C., who, at the age of twenty-three, gave birth to a child on September 13, 1880, and bore a second child on July 2, 1881.

She must have become pregnant twenty-one days after the delivery of her first child.
Superfetation has been known for many centuries; the Romans had laws prescribing the laws of succession in such cases, and many medical writers have mentioned it.

Hippocrates and Aristotle wrote of it, the former at some length.